Patent Publication Number: US-8542205-B1

Title: Refining search results based on touch gestures

Description:
BACKGROUND 
     A large and growing population of users is enjoying entertainment through the consumption of digital content items (or simply “content items”), such as music, movies, images, electronic books, and so on. The users employ various electronic devices to consume such content items. Among these electronic devices are electronic book (eBook) reader devices, cellular telephones, personal digital assistants (PDAs), portable media players, tablet computers, netbooks, and the like. As the quantity of available electronic media content continues to grow, along with increasing proliferation of devices to consume that media content, finding ways to enhance user experience continues to be a priority. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The detailed description is set forth with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The use of the same reference numbers in different figures indicates similar or identical items or features. 
         FIG. 1  illustrates an architecture in which a community of users operates respective client devices to consume content items, such electronic books (eBooks), songs, videos and the like. In this architecture, the client devices and/or a content item service implement techniques to provide context-sensitive reference works (e.g., dictionaries, thesauruses, atlases, etc.) that provide requested information to the users based on a genre of the content item associated with the request, a characteristic of the user, or the like. 
         FIG. 2  is a block diagram of selected modules of an eBook reader device capable of receiving a request for information from a user experiencing a content item, determining a type of reference work entry appropriate for the content item or the user, and providing the information to the user from the determined type of reference work entry. 
         FIG. 3  illustrates an example user interface rendered by the devices of  FIGS. 1 and 2 . Here, the device or the content item service has determined that the eBook currently being read by the user is associated with a “medical” genre. As such, when the user requests a definition for a word within the eBook, the device displays a “medical” definition of the word rather than a standard or other type of definition. 
         FIG. 4  illustrates an example user interface rendered by the device of  FIG. 3  after the user has selected to view “more” definitions of the illustrated word “prognosis.” As shown, in response the device displays definitions of “prognosis” in the medical sense, the standard sense, and the legal sense. 
         FIG. 5  illustrates another example user interface rendered by the devices of  FIGS. 1 and 2 . Here, the device is displaying an article from a periodical relating to “business.” As such, when the user requests to look up in a thesaurus a word within the article, the device displays synonyms and antonyms from a business-related thesaurus entry. 
         FIG. 6  illustrates another example user interface rendered by the devices of  FIGS. 1 and 2 . Here, the device is displaying a sports-related article. As such, when the user requests to look up in an encyclopedia a topic within the article, the device displays information about that topic from a sports-related encyclopedia entry. 
         FIG. 7  is a flow diagram showing a process of classifying a content item according to, for example, a genre and determining, based on the classification, a type of reference work entry to use for the content item when a user requests information associated with a word, phrase, or topic found within the content item. 
         FIG. 8  is a block diagram of selected modules of an example eBook reader device that may implement a touch-sensitive display and that is capable of outputting different reference work entries based on an amount of force applied to the touch-sensitive display. 
         FIG. 9  illustrates an example user interface rendered by the device of  FIG. 8  after a user has made a selection of a word on the touch-sensitive display of the device. Here, the device measures an amount of force of the selection and outputs a particular type of reference work entry based on this measured amount of force. 
         FIG. 10  illustrates an example user interface rendered by the device of  FIG. 8  after the user has increased the amount of force on the selected word. Here, the device outputs a second, different type of reference work entry based on this greater amount of force. 
         FIG. 11  illustrates an example user interface rendered by the device of  FIG. 8  after the user has yet again increased the amount of force on the selected word. Here, the device outputs a third, different type of reference work entry based on this even greater amount of force. 
         FIG. 12  illustrates another example user interface rendered by the device of  FIG. 8  after a user has made a selection of a word on the touch-sensitive display of the device. Here, the device measures an amount of force of the selection and outputs a particular context-sensitive reference work entry based on this measured amount of force. 
         FIG. 13  illustrates another example user interface rendered by the device of  FIG. 8  after the user has increased the amount of force on the touch-sensitive display. Here, the device outputs a second, different context-sensitive reference work entry based on this greater amount of force. 
         FIG. 14  is a flow diagram showing a process of selecting which of multiple reference work entries to output based on an amount of measured force associated with a selection. 
         FIG. 15  illustrates an example user interface rendered by the device of  FIG. 8  after a user has made a selection of a word on the touch-sensitive display of the device. Here, the device outputs a reference work entry based on this selection. 
         FIG. 16  illustrates an example user interface rendered by the device after the user has provided an additional input. In response, the device outputs a second, different reference work entry. This input may include more force on the display, an additional point of contact on the display, activation of a key on a keypad, an oral command spoken by the user or any other type of input. 
         FIG. 17  is a flow diagram showing a process of outputting a first reference work entry in response to receiving a touch selection on a display and, thereafter, outputting a second, different reference work entry after receiving an additional input. 
         FIG. 18  illustrates an example user interface rendered by the device of  FIG. 8  after a user has made a selection of a word on the touch-sensitive display of the device. Here, the device outputs a reference work entry after determining that an amount of force of this selection is less than a threshold force. 
         FIG. 19  illustrates an example user interface rendered by the device of  FIG. 8  after a user has made a selection of a word on the touch-sensitive display of the device. Here, the device enables the user to select a reference work entry to output after the device determines that an amount of force of this selection is greater than a threshold force. 
         FIG. 20  is a flow diagram showing a process of determining whether to output a reference work entry or whether to allow a user to select which reference work entry to output based on an amount of force of a selection. 
         FIG. 21  is a block diagram of selected modules of an example eBook reader device that may implement a touch-sensitive display and that is capable of outputting different content based on an amount of force applied to the touch-sensitive display. 
         FIG. 22  illustrates an example user interface rendered by the device of  FIG. 21  after a user has made a selection of a word within a content item being rendered on the touch-sensitive display of the device. Here, the device may measures an amount of force of the selection and, in some instance, may output a particular type of reference work entry based on this measured amount of force. 
         FIG. 23  illustrates an example user interface rendered by the device of  FIG. 21  after the user has increased the amount of force on the selected word. Here, the device outputs other instances of this word within the illustrated content item based on this greater amount of force. 
         FIG. 24  illustrates an example user interface rendered by the device of  FIG. 21  after the user has yet again increased the amount of force on the selected word. Here, the device outputs other instances of this word within other content items based on this even greater amount of force. 
         FIG. 25  illustrates an example user interface rendered by the device of  FIG. 21  after the user has yet again increased the amount of force on the selected word. Here, the device outputs search results associated with a query comprising the selected word based on this even greater amount of force. 
         FIG. 26  is a flow diagram showing a process of causing display of other instances of a selected term based on a force associated with a selection. 
         FIG. 27  illustrates an example user interface rendered by the device of  FIG. 21  after a user has made a selection of a word within a content item being rendered on the touch-sensitive display of the device. Here, the device requests that the user select whether to view previous or subsequent instances of the selected word within the illustrated content item. 
         FIG. 28  illustrates an example user interface rendered by the device of  FIG. 21  while a user makes a gesture that both selects a word within a content item and requests to view subsequent instances of the selected word within the illustrated content item. 
         FIG. 29  illustrates an example user interface rendered by the device of  FIG. 21  after the gesture made by the user in  FIG. 28 . 
         FIG. 30  is a flow diagram showing a process of causing display of information associated with a portion of a content item in response to receiving a touch selection of the portion on a display and, thereafter, outputting other instances of the portion after receiving an additional input. 
         FIG. 31  illustrates an example user interface rendered by the device of  FIG. 21  after the user selects a word within the illustrated content item. Here, the device outputs search results associated with a query comprising the selected word based on the selection by the user. 
         FIG. 32  illustrates an example user interface rendered by the device of  FIG. 21  after the user provides a greater amount of force to the selected word. Here, the device refines (e.g., narrows) the search results of  FIG. 31  in response to detecting the greater amount of force. 
         FIG. 33  is a flow diagram showing a process of refining search results on a touch-sensitive display based on the device detecting a greater or lesser amount of force on a selected term. 
         FIG. 34  illustrates an example user interface rendered by the device of  FIG. 21  while a user makes a gesture that both selects a word within a content item and requests to narrow illustrated search results associated with the selected word. 
         FIG. 35  illustrates an example user interface rendered by the device of  FIG. 21  after the user performs the gesture of  FIG. 34 . As illustrated, the device has narrowed search results in response to detecting the gesture. 
         FIG. 36  illustrates an example user interface rendered by the device of  FIG. 21  while a user makes a gesture that both selects a word within a content item and requests to expand illustrated search results associated with the selected word. 
         FIG. 37  illustrates an example user interface rendered by the device of  FIG. 21  after the user performs the gesture of  FIG. 36 . As illustrated, the device has expanded or broadened search results in response to detecting the gesture. 
         FIG. 38  is a flow diagram showing a process for refining search results based at least in part on detecting a predefined gesture on a touch-sensitive display. 
     
    
    
     DETAILED DESCRIPTION 
     This disclosure describes techniques for outputting different content on a touch-sensitive display of a device based at least in part on an amount of force applied to the touch-sensitive display. For instance, when a user reads an electronic book (eBook) on a device having a touch-sensitive display, the user may make a selection of a word or phrase within the eBook by touching the display at a location of the word or phrase. In response, the techniques may output information associated with the selected word. For instance, the device may output, in response, a dictionary definition of the selected word, a picture associated with the selected word, synonyms of the selected, or the like. Thereafter, the user may apply a greater or lesser amount of force to the selected word and, in response, the device may output other instances or uses of the selected word. For instance, the device may output other instances of the selected word within the illustrated eBook, other eBooks or content items, or the like. 
     In another example, the techniques described herein may refine search results associated with a particular word or phrase based at least in part on a measured amount of force associated with a selection. For instance, a user may request, via a touch on the touch-sensitive display, that the device perform a search based on a query associated with a selected word or phrase. In response, the device may output search results associated with the search (from a search engine or otherwise). Thereafter, the user may provide an amount of force on the touch-sensitive display that is more or less than the original selection. In response, the device may refine (e.g., expand or narrow) the illustrated search results. In one of many examples, the device may identify a term associated with the rendered eBook and may perform a search based on a query that includes this term in addition to the term selected by the user. 
     This disclosure also describes techniques for outputting different reference work entries based on an amount of force applied to a touch-sensitive display of a device. For instance, when a user reads an electronic book (eBook) on a device having a touch-sensitive display, the user may make a selection of a word or phrase within the eBook by touching the display at a location of the word or phrase. The techniques may then determine which of multiple different reference work entries to output based on a measured amount of force of the selection. For instance, the device may output a dictionary definition of the selected word in response to measuring a first amount of force. Additionally or alternatively, the device may output a thesaurus entry for the word in response to measuring a second, greater amount of force. 
     This disclosure also describes an architecture and techniques for outputting requested information from reference works (e.g., dictionaries, thesauruses, almanacs, atlases, encyclopedias, gazetteers) in a context-sensitive manner. For instance, when a user reads an electronic book (eBook) and requests a definition for a word found within the eBook, the techniques may display a definition for the word that has been selected based on the context of the request. In one example, the techniques may display a definition that corresponds to one or more identified genres of the eBook in which the word appears. In another example, the techniques may display a definition that corresponds to known information about the user, such as a preference of the user or the like. 
     For instance, if a user currently reading a medical-related eBook requests to receive a definition of a word from the eBook, the techniques will display a medical-related definition of the word. If the user reads a science-fiction (sci-fi) eBook, meanwhile, the techniques may display a sci-fi or science-related definition of the word. In each of these instances, the techniques may display more than one definition, with the order of the displayed definitions being based on the classification of the eBook. For instance, the medical definition may be displayed first in instances where the eBook is determined be medical-related. As such, the techniques display information from a reference work, such as the dictionary, in a manner that is more likely to be relevant and of interest to the user. 
     While the discussion below describes these techniques in the context of eBooks rendered on eBook reader devices, these techniques may apply to a variety of different types of content items, such as songs, videos, still images, and so on. Furthermore, the techniques may apply to a variety of different electronic devices, such as personal computers, cellular telephones, personal digital assistants (PDAs), portable media players, tablet computers, netbooks, and the like. 
     In each instance, the techniques may classify a particular content item as being associated with one or more particular genres (e.g., science, science fiction, medicine, business, law, fiction, a particular foreign language, etc.). Before or after the classification, a user experiencing the content item may request some information regarding the content item that may be found within a reference work. For instance, the user may request a definition of a word, synonyms or antonyms for a word, information from an encyclopedia regarding an identified word, phrase, or topic, a map for or directions to an identified location, or the like. In response to receiving this request, the techniques select an entry from the appropriate type of reference work and then output (e.g., visually, audibly, etc.) the reference work entry. 
     For instance, if a user requests information about a particular topic from within the content item, the techniques may select the corresponding encyclopedia entry based on the genre of the content item. For instance, if the user currently experiences a sports-themed content item and the user requests information regarding the topic “bat,” the techniques may output information regarding “bats” from a sports-themed encyclopedia. This information will likely discuss a round, elongated object for hitting a ball. If, however, the user currently experiences an animal-related content item and the user makes the same request, the techniques may output an encyclopedia entry from an animal-related encyclopedia. This information will likely discuss the nocturnal mammal. 
     While the above example describes referencing discrete reference works (here, encyclopedias), the techniques may instead reference a single reference work that includes multiple different types of entries (e.g., sports-related, animal-related, medical, etc.). For instance, a single encyclopedia may include an entry for “bat” in the sports sense and an entry for “bat” in the animal sense. Here, the techniques may display one or both of the definitions in a manner based on the identified genre of the content item. 
     The discussion begins with a section, entitled “Context-Sensitive Reference Works,” that includes numerous sub-sections. A first sub-section is entitled “Example Architecture” and describes one example architecture and several example components that implement the techniques introduced above. Next, a sub-section entitled “Example eBook Reader Device” follows, and describes example components of one type of device that may implement context-sensitive reference works. A sub-section entitled “Example User Interfaces” follows, describing examples of user interfaces (UIs) that may be served to and rendered at the client devices of  FIG. 1 . The discussion then moves on to illustrate and describe an “Example Process” for implementing the described techniques. 
     The discussion also includes a second section, entitled “Surfacing Reference Work Entries on Touch-Sensitive Displays,” that also includes numerous sub-sections. A first sub-section is entitled “Example eBook Reader Device” and describes example components of one type of device that may implement the techniques in this section. A sub-section entitled “Example User Interfaces and Processes” follows. 
     The discussion also includes a third section, entitled “Surfacing Content Based on Touch Gestures” that, like the preceding sections, includes numerous sub-sections. A first sub-section is entitled “Example eBook Reader Device” and describes example components of one type of device that may implement the techniques in this section. A sub-section entitled “Example User Interfaces and Processes for Surfacing Other Instances of a Selected Term” follows. Thereafter, the discussion includes a sub-section entitled “Example User Interfaces and Processes for Refining Search Results,” before the discussion ends with a brief conclusion. 
     This brief introduction, including section titles and corresponding summaries, is provided for the reader&#39;s convenience and is not intended to limit the scope of the claims, nor the proceeding sections. Furthermore, the techniques described above and below may be implemented in a number of ways and in a number of contexts. Several example implementations and contexts are provided with reference to the following figures, as described below in more detail. However, the following implementations and contexts are but a few of many. 
     Context-Sensitive Reference Works 
     Architectural Environment 
       FIG. 1  illustrates an example architecture  100  in which a community of users  102  operates respective client devices  104 ( 1 ),  104 ( 2 ),  104 ( 3 ), . . . ,  104 (M) to consume content items, such electronic books (eBooks), songs, videos, still images and the like. In this architecture, the client devices  104  and/or a content item service  106  implement techniques to provide context-sensitive reference works (e.g., dictionaries, thesauruses, atlases, etc.) that provide requested information to the users based on a genre of the content item associated with the request, a characteristic of the requesting user, or the like. 
     The client devices  104  are variously configured with different functionality to enable consumption of one or more types of contents items of any type or format including, for example, electronic texts (e.g., documents of any format, electronic periodicals, such as digital magazines and newspapers, etc.), digital audio (e.g., music, audible books, etc.), digital video (e.g., movies, television, short clips, etc.), images (e.g., art, photographs, etc.), and multi-media content. The terms “electronic book” and/or “eBook”, as used herein, include electronic or digital representations of printed works, as well as digital content that may include text, multimedia, hypertext, and/or hypermedia. Examples of printed and/or digital works include, but are not limited to, books, magazines, newspapers, periodicals, journals, reference materials, telephone books, textbooks, anthologies, instruction manuals, proceedings of meetings, forms, directories, maps, web pages, etc. 
       FIG. 1  illustrates that the client devices  104  operated by users of the user community  102  may comprises eBook reader devices (e.g., devices  104 ( 1 ) and  104 ( 2 )), laptop computers (e.g., device  104 ( 3 )), multifunction communication devices (e.g., device  104 (M)), portable digital assistants (PDAs), wireless headsets, entertainment systems, portable media players, tablet computers, cameras, video cameras, netbooks, notebooks, desktop computers, gaming consoles, DVD players, media centers, or any other type of device. 
     In the architecture  100 , the client devices may receive, over a network  108 , one or more content items for presentation on the devices from the content item service  106 . The network  108  is representative of any one or combination of multiple different types of networks, such as the Internet, cable networks, cellular networks, wireless networks, and wired networks. One example of a wireless technology and associated protocols is the Wireless Fidelity (WiFi) wireless networking technologies defined according to IEEE 802.11 standards, while another example is a cellular network. 
     As illustrated, the content item service  106  is embodied as one or more servers that collectively have processing and storage capabilities to receive requests for content items from the devices, such as the eBook reader device  104 ( 1 ). The servers of the content item service  106  may be embodied in any number of ways, including as a single server, a cluster of servers, a server farm or data center, and so forth, although other server architectures (e.g., mainframe) may also be used. Alternatively, the content item service  106  may be embodied as a client device, such as desktop computer, a laptop computer, an eBook reader device and so forth. In some implementations, for instance, some or all of the elements of content item service  106  illustrated in  FIG. 1  may reside on the client devices  104 . 
     In the illustrated example, the content item service  106  includes a content item distribution system  110 , a content item database  112 , and a content item classifier  114 . The content item distribution system  110  may support distribution of content items (e.g., online retailing via a website) to the client devices  104 . In some implementations, the servers store the content items in the content item database  112 , although in other implementations, the servers merely facilitate purchase and delivery of content items stored in other locations. 
     The content item classifier  114 , meanwhile, serves to classify content items by, for example, genre. For instance, the classifier  114  may classify content items as relating to fiction, non-fiction, historical, science, science fiction, medicine, business, law, sports, animals, geography, computer science, engineering, chemistry, mathematics, a particular language or any other type of genre, category, or classification. To classify these content items, the classifier  114  may reference a prior categorization of the content items within, for example, the content item database  112 . Or, the classifier may classify these content items in other ways, as discussed in detail below. 
     Furthermore, the content item classifier  114  may classify content items as relating to multiple different genres. For instance, an eBook that includes multiple sections may be associated with different genres corresponding to the different sections of the book. A textbook, for instance, may include a section classified as relating to mathematics, a section classified as relating to science, and a section classified as relating to medicine. A single section or an entire eBook may also be classified as relating to multiple genres. 
     As discussed in detail below, these genre classifications may be used to determine which category of reference work entry to use when receiving a request for information from a user. For instance, if a user reading the afore-mentioned textbook requests a definition for a word found within the science section of the book, the device of the user may display a science-related dictionary entry (alone or more prominently than other definitions). 
     The content item classifier  114  may classify content items in a multitude of ways. As illustrated, the content item classifier  114  includes a contents analysis module  116 , a feedback module  118 , and a user analysis module  120 . The contents analysis module  116  may classify content items with reference to the actual contents of the item. Using an eBook as an example, this module  116  may scan the text of the eBook to identify key words and may then compare these identified key words to known, pre-compiled sets of key words associated with different genres. For example, the module  116  may scan contents of an eBook and may identify that the most-frequently used words of the eBook include “medicine,” “doctor,” “Dr.,” “disease,” and “hospital.” As such, the module  116  may compare these key words to sets of key words associated with different genres before concluding that this book should be classified as being within the medical genre. Similarly, the module  116  may analyze images or sounds within a content item and may compare these images or sounds to known sets of images or sounds associated with identified genres. 
     In some instances, this module  116  may weight certain words more heavily than others. For instance, the module  116  may weight the words of the title more heavily than the words within the chapters of the book. Similarly, the module  116  may assign a larger weight to the name of the author, the identity of the publisher, and the like. 
     The feedback module  118 , meanwhile, serves to classify content items in whole or in part based upon received feedback. For instance, these techniques may include querying human users as to the genre of a content item and using responses from the users as input in determining the genre(s) of the respective content item. Furthermore, this module  118  may also track user actions in order to receive this feedback. For instance, envision that a user requests a definition found within a particular eBook for the term “boil.” Envision also that the classifier  114  has classified this eBook as relating to science and, as such, the user&#39;s device displays a science definition of the term boil, explaining that “boiling” refers to when a liquid changes state to a gas. However, feedback module  118  may determine (e.g., via an indication received over the network  108 ) that the user requested to see a different definition of the term “boil” (e.g., a medical definition). In this instance, the feedback module  118  may deduce that the eBook should have been classified as being of the “medical” genre rather than the “science” genre. 
     In some instances, the classifier  114  may assign a confidence level to a particular genre associated with a content item and may alter this genre based on feedback received at the feedback module  118 . For instance, the classifier may determine that the eBook from this example above is 53% likely to be primarily of a “science” genre and 47% likely to be primarily of a “medical” genre. After receiving feedback similar to the feedback from the user discussed immediately above, these percentages may change such that the classifier  114  now judges that the eBook is more likely to relate to medicine than pure science. As such, the classifier  114  may change the assigned genre to “genre” (or may change the primary genre to “medical” while marking “science” as a secondary genre). 
     The user analysis module  120 , meanwhile, may function to classify content items in whole or in part based upon the identity of the user experiencing the media item. For instance, when the content item distribution system  110  downloads an eBook to the eBook reader device  104 ( 1 ), the module  120  may analyze known information about the user associated with the device by, for instance, referencing a user profile stored in an account of the user at the content item service  106 . The module  120  may then use this known information about the user to help deduce the genre of the eBook. 
     For instance, envision that the user associated with the eBook reader device  104 ( 1 ) often purchases eBooks, audio items, and the like that are classified as being of the “medical” genre. Therefore, when attempting to determine the genre of a new eBook purchased at the device  104 ( 1 ), the module  120  may more heavily weight the chances of this eBook being related to medicine. The user analysis module  120  may similarly use any other known information about the user to help classify content items, including a location of the user, demographic information of the user, an address of the user, and the like. 
     With information from some or all of the modules  116 ,  118 , and  120 , the content item classifier  114  may classify content items as belonging to one or more genres. For instance, individual sections of content items (e.g., chapters, individual songs or tracks, etc.) may each be associated with one or more genres, or an entire content item may be associated with a single or multiple genres. In each instance, the determined genre(s) is helpful to determine the appropriate type or category of reference work entry to use when a user requests information regarding a word, phrase, or topic within the corresponding content item. 
       FIG. 1 , for instance, illustrates that the eBook reader device  104 ( 1 ) currently displays a fictitious eBook  122  entitled “Secrets to Internal Medicine” by a fictitious author “Dr. Grace Bradley,” which the device  104 ( 1 ) may have downloaded from the content item service  106 .  FIG. 1  also illustrates that the content item database  112  stores the same eBook  122 . In addition,  FIG. 1  illustrates that the content item classifier  114  has classified this eBook  122  as relating a particular genre  124 . Here, the classifier  114  has determined that the eBook relates to medicine and has classified this book accordingly. The content item database  112  may similarly store multiple other content items along with a notation of the genre(s) of each of these other items. 
     In this example, the user of the eBook reader device  104 ( 1 ) has selected (via a highlight  126 ) a particular word (“prognosis”) from the eBook  122 . In response, the eBook reader device  104 ( 1 ) displays a definition  128  of the selected word. Here, the definition  128  of the word comes from a medical dictionary entry, which corresponds to the classification of the eBook  16  as being related to the “medical” genre. As such, this definition  128  states that a “prognosis” is “a forecast of the probable course and/or outcome of a disease.” While this example describes a dictionary, other implementations may employ other types or categories of reference works, a few examples of which are discussed below. 
     Example eBook Reader Device 
       FIG. 2  illustrates example components that might be implemented in the eBook reader device  104 ( 1 ) of  FIG. 1  that displays information provided by context-sensitive reference works, such as dictionaries or the like. In this example, the eBook reader device  104 ( 1 ) is a dedicated, handheld eBook reader device, although other electronic devices may implement these techniques and, hence, may include some of the functionality described herein. 
     In a very basic configuration, the eBook reader device  104 ( 1 ) includes one or more processing units  202  and memory  204 . Depending on the configuration of a dedicated eBook reader device  104 ( 1 ), the memory  204  (and other memories described throughout this document) is an example of computer storage media and may include volatile and nonvolatile memory. Thus, the memory  204  may include, but is not limited to, RAM, ROM, EEPROM, flash memory, or other memory technology, or any other medium which can be used to store media items or applications and data which can be accessed by the eBook reader device  104 ( 1 ). 
     The memory  204  may be used to store any number of functional components that are executable on the processing unit(s)  202 , as well as data and content items that are rendered by the eBook reader device  104 ( 1 ). Thus, the memory  204  may store an operating system and an eBook storage database to store one or more content items  206 , such as eBooks, audio books, songs, videos, still images, and the like. The memory  204  may further include a memory portion designated as an immediate page memory to temporarily store one or more pages of an electronic book. The pages held by the immediate page memory are placed therein a short period before a next page request is expected. 
     The term “page,” as used herein, refers to a collection of content that is presented at one time in a display of the eBook reader device  104 ( 1 ). Thus, a “page” may be understood as a virtual frame of the content, or a visual display window presenting the content to the user. Thus, “pages” as described herein are not fixed permanently, in contrast to the pages of published “hard” books. Instead, pages described herein may be redefined or repaginated when, for example, the user chooses a different font for displaying the content in the first display. In addition to pages, the terms “page views”, “screen views”, and the like are also intended to mean a virtual frame of content. 
     An interface module  208  may also be provided in memory  204  and may be executed on the processing unit(s)  202  to provide for user operation of the device  104 ( 1 ). One feature of the interface module  208  allows a user to request to receive information from a reference work regarding a word, phrase, or topic found within one of the content items  206 . For instance, the interface module  208  may allow the user to request a definition of a word from a dictionary, synonyms from a thesaurus, a map from an atlas, and the like. 
     The interface module  208  may facilitate textual entry of request (e.g., via a cursor, controller, keyboard, etc.), audible entry of the request (e.g., via a microphone), or entry of the request in any other manner. The interface module  208  may provide menus and other navigational tools to facilitate selection and rendering of the content items  206 . The interface module  208  may further include a browser or other application that facilitates access to sites over a network, such as websites or online merchants. 
     A content presentation application  210  renders the content items  206 . The content presentation application  210  may be implemented as various applications depending upon the content items. For instance, the application  210  may be an electronic book reader application for rending electronic books, or an audio player for playing audio books or songs, or a video player for playing video, and so forth. 
     The memory  204  may also store user credentials  212 . The credentials  212  may be device specific (set during manufacturing) or provided as part of a registration process for a service. The credentials may be used to ensure compliance with DRM aspects of rendering the content items  206 . 
     The memory  204  also stores one or more reference works  214 , such as one or more dictionaries, thesauruses, encyclopedias, atlases, gazetteers, and the like. In some instances, the memory  204  stores multiple categories of a particular kind of reference work. For instance, the memory  204  may store a standard dictionary (e.g., Merriam-Webster® English Dictionary), a medical dictionary, a legal dictionary, a science dictionary, a science-fiction dictionary, an engineering dictionary, a foreign language dictionary, a business dictionary, a chemistry dictionary, a mathematics dictionary, and the like. In other instances, a single kind of reference work may contain multiple reference work entry types. For instance, a single dictionary may store, for one or more of the words therein, a standard dictionary entry, a medical dictionary entry, a legal dictionary entry, a science dictionary entry, and the like. 
       FIG. 2  further illustrates that the memory  204  stores a feedback module  216  that is executable on the processing unit(s) to receive user feedback regarding an outputted reference work entry or a classified genre of a content item. As discussed above, this feedback may be used to help re-classify the genre associated with the content item. 
     The eBook reader device  104 ( 1 ) also stores a reference entry selection module  218  that is executable on the processing unit(s) to select a particular type of reference work entry based on a genre of a content item, a characteristic of a user, or the like. For instance, this module  218  may store or reference a table that maps “content item genres” to “reference work entry types.” Therefore, when the content presentation application  210  outputs a content item of a particular genre and the user requests some reference work information associated with a word, phrase, or topic therein, the module  218  may reference this table to determine the type of entry to output. In some instances, the reference entry selection module  218  may reside on the content item service  106  or in another location, in which case the eBook reader device  104 ( 1 ) may access the module  218  over the network  108 . 
     In the example of  FIG. 1 , the module  218  may determine that the application  210  should display a medical definition when receiving a request for a word within an eBook that has been categorized as “medical” in nature. This table may similarly map a “legal” genre to a “legal” reference work entry type, a “sci-fi” genre to a “science” reference work entry type, a “historical fiction,” “British lit” and the like to a “standard” reference work entry type, and so on. In some instances, this table may map combinations of genres to reference work entry types. For instance, the table may map an eBook that is associated with both a “medical” genre and a “mystery” genre to a “standard” reference work entry type rather than a “medical” reference work entry type. It is to be appreciated, however, that  FIG. 2  simply illustrates several example mappings, and that any type of content item genre may map to any type of reference work entry type in certain implementations. 
       FIG. 2  further illustrates that the eBook reader device  104 ( 1 ) may include a display  220 , which may be passive, emissive or any other form of display. In one implementation, the display uses electronic paper (ePaper) display technology, which is bi-stable, meaning that it is capable of holding text or other rendered images even when very little or no power is supplied to the display. Some example ePaper-like displays that may be used with the implementations described herein include bi-stable LCDs, MEMS, cholesteric, pigmented electrophoretic, and others. In other implementations, or for other types of devices, the display may be embodied using other technologies, such as LCDs and OLEDs, and may further include a touch screen interface. In some implementations, a touch sensitive mechanism may be included with the display to form a touch-screen display. 
     The eBook reader device  104 ( 1 ) may further be equipped with various input/output (I/O) components  222 . Such components may include various user interface controls (e.g., buttons, a joystick, a keyboard, etc.), audio speakers, connection ports, and so forth. 
     A network interface  224  supports both wired and wireless connection to various networks, such as cellular networks, radio, WiFi networks, short range networks (e.g., Bluetooth), IR, and so forth. The network interface  224  may allow a user of the device  104 ( 1 ) to download content items from the content item service  106 , may allow the feedback module  216  to provide received feedback to the service  106 , and the like. 
     The eBook reader device  104 ( 1 ) also includes a battery and power control unit  226 . The battery and power control unit operatively controls an amount of power, or electrical energy, consumed by the eBook reader device. Actively controlling the amount of power consumed by the reader device may achieve more efficient use of electrical energy stored by the battery. 
     The eBook reader device  104 ( 1 ) may have additional features or functionality. For example, the eBook reader device  104 ( 1 ) may also include additional data storage devices (removable and/or non-removable) such as, for example, magnetic disks, optical disks, or tape. The additional data storage media may include volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information, such as computer readable instructions, data structures, program modules, or other data. 
     Various instructions, methods and techniques described herein may be considered in the general context of computer-executable instructions, such as program modules, executed by one or more computers or other devices. Generally, program modules include routines, programs, objects, components, data structures, etc. for performing particular tasks or implement particular abstract data types. These program modules and the like may be executed as native code or may be downloaded and executed, such as in a virtual machine or other just-in-time compilation execution environment. Typically, the functionality of the program modules may be combined or distributed as desired in various embodiments. An implementation of these modules and techniques may be stored on or transmitted across some form of computer readable media. 
     Example User Interfaces 
       FIGS. 3-6  illustrate example user interfaces that the eBook reader device  104 ( 1 ) (and the other client devices of the architecture  100 ) may render in accordance with the techniques described above. While these figures illustrates a few example interfaces it is to be appreciated that numerous other types of interfaces displaying information from numerous other types of reference works may be implemented using the described techniques. 
       FIG. 3  illustrates the example user interface described above with reference to  FIG. 1 . Here, the eBook reader device  104 ( 1 ) or the content item service  106  has determined that the eBook  122  currently being read by the user is associated with a “medical” genre. As such, when the user requests a definition for a word within the eBook, the device displays a “medical” definition of the word rather than a standard or other type of definition. 
     Specifically,  FIG. 3  illustrates that the user has selected (e.g., via a keyboard, cursor, touch screen, etc.) the word “prognosis,” as illustrated by the highlight  126 . While the user selects a word in this example, the user may select a phrase in other embodiments. In response to the selection, the device  104 ( 1 ) displays the medical definition  128  of this word. As illustrated, this definition  128  includes an indication  302  that this definition is in fact the medical definition, rather than another type of definition (e.g., a standard definition, a science definition, etc.). 
     In this example, the eBook reader device  104 ( 1 ) may display a definition from a dictionary when the user selects a word, although in other implementations the device may display synonyms from a thesaurus, information from an encyclopedia, or information any other reference work type. In still other implementations, the device  104 ( 1 ) may prompt the user to select the type of the reference work from which the device should display information. 
       FIG. 3  also illustrates that the definition  128  includes an icon  304  (“More”) that, when selected, allows the user to view additional definitions of the word “prognosis.” 
       FIG. 4  illustrates an example user interface rendered by the eBook reader device  104 ( 1 ) after the user has selected to view “more” definitions of the word “prognosis.” As shown, in response the device displays the definition  128  of this word in the medical sense first, followed by a definition  402  of the word in a standard sense, and a definition  404  of the word in a legal sense. Here, the order of the list is also based on the genre of the eBook, with the medical definition appearing first. In some instances, one or both of the feedback modules  118  and  216  may use the user&#39;s selection of the icon  304  as an indication that the eBook or the currently displayed portion of the eBook may need to be re-classified. For instance and as discussed above, this selection may alter the confidence level associated with the currently associated genre. 
       FIG. 5  illustrates another example user interface rendered by the eBook reader device  104 ( 1 ). Here, the device currently displays an eBook  502  comprising a periodical article that has been determined to relate the genre “business.” As such, when the user requests information from a reference work regarding a word, phrase, or topic from the eBook  502 , the device may display a reference work entry associated with the genre “business.” 
     Here, for instance, the user requests (either explicitly or via default settings) to look up the word “bear” in a thesaurus, as indicated by a highlight  504 . In response, the eBook reader device  104 ( 1 ) displays an entry  506  from a thesaurus, the entry comprising synonyms and antonyms. As illustrated, an indication  508  indicates that this entry corresponds to a “business” use of the term “bear,” as the synonyms include “pessimist, cynic, defeatist, misanthrope,” while the antonyms include “bull, optimist.” This is contrasted with the standard use of the term “bear” in the English language, having synonyms of bear “stand, stomach, tolerate, abide” and the like. However, by displaying a business-related thesaurus entry when the user reads a business-related eBook, the device  104 ( 1 ) is more likely to provide the user with the information that she seeks. Furthermore, the device  104 ( 1 ) also displays the “more” icon  304  to allow the user to view other thesaurus entry types associated with the word “bear” (e.g., the standard use entry, an entry related to animals, etc.). 
       FIG. 6  illustrates another example user interface rendered by the eBook device  104 ( 1 ). Here, the device  104 ( 1 ) is displaying an eBook  602  in the form of an article that has been determined be associated with a “sports” genre. Here, the user requests to look up the topic “bat” in an encyclopedia, as indicated by a highlight  604 . In response, the device  104 ( 1 ) displays an entry  606  from a sports-related encyclopedia that explains the history and importance of a “baseball bat.” The eBook device  104 ( 1 ) also displays an indication  608  that the entry  606  resides in a sports-related encyclopedia, or that the entry is sports-related entry in a general encyclopedia. 
     Again, the device also displays the “more” icon that, when selected, causes the device to display other articles associated with the term “bat,” such as an article about the nocturnal mammal. In instances where the currently displayed eBook  602  has user been classified as related to an “animal” genre, the device  104 ( 1 ) may instead display the animal-related encyclopedia entry first, rather than the illustrated sports-related entry  606 . 
     Example Process 
       FIG. 7  illustrates an example process  700  for implementing the techniques described above of providing context-sensitive reference work entries. This process is illustrated as a logical flow graph, each operation of which represents a sequence of operations that can be implemented in hardware, software, or a combination thereof. In the context of software, the operations represent computer-executable instructions that, when executed by one or more processors, perform the recited operations. Generally, computer-executable instructions include routines, programs, objects, components, data structures, and the like that perform particular functions or implement particular abstract data types. The order in which the operations are described is not intended to be construed as a limitation, and any number of the described operations can be combined in any order and/or in parallel to implement the process. 
     For discussion purposes, the process  700  is described with reference to the architecture  100  of  FIG. 1 , although other architectures may implement this process. 
     Process  700  includes an operation  702 , which represents classifying a content item as belonging to one or more genres, such as one or more of the genres discussed above. This analyzing may include one or a combination of sub-operations  702 ( 1 ),  702 ( 2 ), and  702 ( 3 ). Classifying a content item may include, for instance, analyzing contents of the content item at sub-operation  702 ( 1 ). This may include analyzing a content item for key words and comparing these key words to sets of key words associated with different respective genres. Sub-operation  702 ( 2 ), meanwhile, may include referencing a prior categorization of the content item, such as from an electronic catalog of content items. Finally, sub-operation  702 ( 3 ) may include referencing feedback regarding the content item itself, as discussed above. 
     After classifying the item, an operation  704  represents determining a reference work entry to use for the content item based at least in part on the classified genre of the item. For instance, if the item has been classified as “legal,” operation  704  may determine that a “legal” reference work entry should be used. Conversely, if the reference work is classified as “thriller,” then operation  704  may determine that a “standard” reference work entry should be used. 
     Next, an operation  706  represents receiving a request for information found within a reference work regarding a word, phrase, or topic found within the content item. This may include, for example, receiving a request for a definition of a word from a dictionary, synonyms or antonyms for the word from a thesaurus, information regarding a topic from an encyclopedia, a map from an atlas, or the like. 
     Operation  708 , meanwhile, represents selecting a reference work entry from the determined type of reference work entry type. For instance, after the user requests to receive a definition of the word “prognosis” found within a medical-related book, operation  708  may select the medical definition of “prognosis.” Next, an operation  710  represents outputting (visually, audibly, etc.) the selected reference work entry, such as the medical definition of the term “prognosis.” Again, this outputting may comprise outputting multiple definitions of the word in an order based at least in part on the classified genre(s) of the content item. For instance, operation  710  may output multiple definitions of the word “prognosis,” with the medical definition being displayed first or more prominently in the list relative to the other definitions. 
     Operation  712  represents querying whether feedback (e.g., user feedback) has been received in response to the output of the reference work entry. For instance, operation  712  may query whether the user decided to view additional definitions of the word “prognosis.” If so, then this feedback is fed back to the classification block to potentially alter the classification of the content item. If no feedback is received, then the process  700  ends at operation  714 . 
     Surfacing Reference Work Entries on Touch-Sensitive Displays 
     Example eBook Reader Device 
       FIG. 8  is a block diagram of selected modules of an eBook reader device  800  that may implement a touch-sensitive display and that is capable of outputting different reference work entries based on an amount of force applied to the touch-sensitive display. The illustrated eBook reader device  800  may include several similar or identical components as the eBook reader device  104 ( 1 ) described above. 
     In this example, the eBook reader device  800  is a dedicated, handheld eBook reader device, although other electronic devices may implement these techniques and, hence, may include some of the functionality described herein. For instance, mobile telephones, tablet computers, laptop computers, desktop computers, personal media players, portable digital assistants (PDAs), or any other type of electronic device may implement the components and techniques described below. 
     In a basic configuration, the example eBook reader device  800  includes one or more processing units  802  and memory  804 . In addition, the eBook reader device  800  may include a touch sensor  806  that enables a user of the device to operate the device via touch inputs. In some instances, the touch sensor  806  and the display  220  are integral to provide a touch-sensitive display that displays content items (e.g., eBooks) and allows users to navigate the content items via touch inputs on the display. 
     The memory  804  may be used to store any number of functional components that are executable on the processing unit(s)  802 , as well as data and content items that are rendered by the eBook reader device  800 . Thus, the memory  804  may store an operating system and an eBook storage database to store the one or more content items  206  described above, such as eBooks, audio books, songs, videos, still images, and the like. 
     A content presentation application  210  renders the content items  206 . The content presentation application  210  may be implemented as various applications depending upon the content items. For instance, the application  210  may be an electronic book reader application for rending electronic books, an audio player for playing audio books or songs, a video player for playing video, and so forth. 
     The memory  804  may also store user credentials  212 . The credentials  212  may be device specific (set during manufacturing) or provided as part of a registration process for a service. The credentials may be used to ensure compliance with DRM aspects of rendering the content items  206 . 
     The memory  804  also stores (persistently or temporarily) one or more reference works  214 , such as one or more dictionaries, thesauruses, encyclopedias, atlases, gazetteers, and the like. In some instances, the memory  204  stores multiple categories of a particular kind of reference work. For instance, the memory  204  may store a standard dictionary (e.g., Merriam-Webster®English Dictionary), a medical dictionary, a legal dictionary, a science dictionary, a science-fiction dictionary, an engineering dictionary, a foreign language dictionary, a business dictionary, a chemistry dictionary, a mathematics dictionary, and the like. In other instances, a single kind of reference work may contain multiple reference work entry types. For instance, a single dictionary may store, for one or more of the words therein, a standard dictionary entry, a medical dictionary entry, a legal dictionary entry, a science dictionary entry, and the like. In still other instances, the device may store a dictionary that accompanies a particular eBook. For instance, the device may store a dictionary that a publisher of a particular eBook creates for that particular eBook or for a particular series of eBooks. 
     The memory  804  may also include the interface module  208  that, as described above, provides for user operation of the device  104 ( 1 ). One feature of the interface module  208  allows a user to request to receive information from a reference work regarding a word, phrase, or topic found within one of the content items  206 . For instance, the interface module  208  may allow the user to request a definition of a word from a dictionary, synonyms from a thesaurus, a map from an atlas, and the like. 
     The interface module  208  may facilitate textual entry of request (e.g., via a cursor, controller, keyboard, etc.), audible entry of the request (e.g., via a microphone), or entry of the request in any other manner. 
     The memory  804  also stores a touch-input controller  808  to detect touch inputs received via the touch sensor  806  and, in some instances to measure of a force of the touches. In some instances, the touch-input controller  808  is configured to detect multiple touches on the touch sensor  806  as well as to measure an amount of force of each of the touches. 
     The eBook reader device  800  also stores a reference entry selection module  810  that is executable on the processing unit(s) to select a particular type of reference work entry in response to receiving an indication of a touch input. For instance, in response to the user selecting a particular portion of a rendered content item via a touch input, the reference entry selection module  810  may select a particular type of reference work entry to output based on a measured force of the touch input. For example, if a user selects a particular word on the touch-sensitive display, the module  810  may map the amount of force of the touch to one of multiple different reference work entries. 
     In one specific example, the module  810  outputs a dictionary definition of the word in response to the user providing a first amount of force, a thesaurus entry for the word in response to the user providing a greater amount of force, and an encyclopedia entry for the word in response to the user providing an even greater amount of force. Or, the module  810  may select and output multiple different reference work entries within a same type of reference work. For instance, the module  810  may output a medical definition of a word in response to a touch input having a first force, a standard definition of the word in response to a touch input having a greater force, and a legal definition of the work in response to a touch input having an even greater force. 
     As such, the reference entry selection module  810  allows a user to toggle through multiple reference work entries for a particular word, phrase, or topic by providing additional force to the touch-sensitive display. The order and substance of the outputted reference work entries may be configurable by a user of the device, may be set by a publisher or distributor of a corresponding content item, or the like. Furthermore, while a few example configurations have been described, multiple other configurations may also be implemented. 
     In some instances, the reference entry selection module  810  selects a reference work entry to output based on factors in addition to a first touch input. For instance, a user may select a word or other portion of a content item on touch-sensitive display and, in response, the module  810  may select and output a first reference work entry. Thereafter, the user may provide an additional input and, in response, the module  810  may select and output a different reference work entry. 
     The additional input may comprise an additional touch, the user activating a button on the keypad, the user orally stating a command, or any other type of user input. As such, the user is able to toggle through multiple reference work entries by providing an input to the touch sensor  806  and thereafter providing additional inputs to the touch sensor  806  and/or the interface module  208 . For instance, where the touch sensor  806  is capable of detecting and interpreting multiple coincident touches, the user may place a first finger on the touch sensor  806  to cause display of a first reference work entry and then may toggle through other reference work entries by tapping another finger on the touch sensor  806 . 
     In addition, the reference entry selection module  810  may select a reference entry to output based on other characteristics. For instance, the module  810  may select a particular entry to output based on a current location of the device, as determined by a GPS system resident on the device, signal triangulation, or any other location-sensing method. 
       FIG. 2  further illustrates that the eBook reader device  800  may include the display  220 , which may be passive, emissive or any other form of display as discussed above. Also as discussed above, the display  220  and the touch sensor  806  may couple to form a touch-sensitive display. That is, the touch sensor  806  may reside underneath or above the display  220  in some instances, or may reside adjacent to the display in other instances. 
     The eBook reader device  800  may further be equipped with various input/output (I/O) components  222 . Such components may include various user interface controls (e.g., buttons, a joystick, a keyboard, etc.), audio speakers, connection ports, and so forth. In addition, a network interface  224  supports both wired and wireless connection to various networks, such as cellular networks, radio, WiFi networks, short range networks (e.g., Bluetooth), IR, and so forth. The network interface  224  may allow a user of the device  800  to download content items from the content item service  106 . 
     The eBook reader device  800  also includes a battery and power control unit  226 . The battery and power control unit operatively controls an amount of power, or electrical energy, consumed by the eBook reader device. Actively controlling the amount of power consumed by the reader device may achieve more efficient use of electrical energy stored by the battery. 
     Example User Interfaces and Processes 
       FIG. 9  illustrates an example user interface rendered by the device  800  of  FIG. 8 . As illustrated, the device includes a touch-sensitive display  902  that renders an eBook  904 . During rendering of the eBook  904 , a user makes a selection of a word on the touch-sensitive display  902 , as illustrated by the highlight  126 . In response, the touch-input controller  808  of the device  800  measures an amount of force  906  of the selection and provides this measured amount to the reference entry selection module  810 . This module  810  may then map this particular amount of force to a particular type of reference work entry to output. For instance, the module  810  may output a first type of reference work entry for a touch-input having a measured force within a first range, a second type of reference work entry for a touch-input having a measured force within a second range, and so forth. 
     In other instances, meanwhile, the controller  808  may measure the amount of force  906  of the initial touch and may use this amount as a baseline for future touches. For instance, the device  800  may select and output a first type of reference work entry in response to detecting a first touch, regardless of the amount of force of the touch. Thereafter, the device  800  may output other reference work entries in response to detecting touches having greater or lesser forces than the initial “baseline” touch. 
     In either instance, once the module  810  selects a reference work entry type, the module  810  may output the entry to the user. In the illustrated example, the module  810  has overlaid the entry onto the touch-sensitive display  902 , although other implementations may output the entry in other ways. In this example, the reference work selection module  810  has selected, based on the amount of force  906  of the touch input, a dictionary entry  908  to output on the display. As such,  FIG. 9  illustrates that the device  800  outputs the dictionary entry  908  for the selected word “Mammal.”  FIG. 9  also illustrates that the entry  908  provides an indication  910  of the source of the reference work entry. 
       FIG. 10  illustrates an example user interface rendered by the device  800  after the user has increased the amount of force on the selected word. As illustrated, the user now selects the word “mammal” with an amount of force  1002  that is greater than the amount of force  906 . The user may or may not have maintained contact with the touch-sensitive display  902  between the applications of these two forces. In response to the second input of the user, the touch-input controller  808  has detected the greater amount of force  1002  and provided this information to the reference entry selection module  810 . In response, the module  810  has mapped this amount of force to a particular reference work entry. 
     Here, the module  810  has selected a thesaurus entry  1004  for output on the touch-sensitive display  902 . As illustrated, the thesaurus entry includes an indication  1006  of the source of entry, along with both synonyms and antonyms of the word “mammal.” While  FIG. 10  illustrates that the device  800  outputs the thesaurus entry  1004  in response to detecting the amount of force  1002  on the location of the display  902  associated with the word “mammal,” other implementations may output any other type of reference work entry. In addition, other implementations may output the thesaurus entry in response to detecting a lesser amount of force. 
       FIG. 11  illustrates yet another example user interface rendered by the device  800  after the user has yet again provided an input having an increased amount of force  1102  on the selected word “mammal.” After the touch-input controller  808  measures the increased force  1102  and provides this information to the reference entry selection module  810 , the module  810  selects a third, different type of reference work entry to output on the device. In the illustrated example, the device  800  outputs an encyclopedia entry  1104  for the word “Mammal,” which again includes an indication  1106  of the source of the entry. 
     With use of the described techniques, the user of the device  800  is able to toggle through multiple different reference work entries associated with a particular word, phrase, image, or other portion of a content item. For instance, the user may toggle through a dictionary entry, a thesaurus entry, an encyclopedia entry, and/or any other type of reference work entry by altering the amount of force applied to the touch-sensitive display  902 . In addition, the device  800  may store locally some or all of the underlying reference works, or the device  800  may request and receive the surfaced entries over a network on an on-demand basis. 
       FIG. 12  illustrates another example user interface rendered by the device  800 . Here, the touch-sensitive display  902  of the device  800  renders the eBook  504  discussed with reference to  FIG. 5  above. Here, the user selects (via a touch input) the word “bear” on the display  902 , as indicated by the highlight  126 . In response, the touch-input controller  808  measures an amount of force  1202  of the selection. Based at least partly on the amount of force  1202  of the selection, the reference entry selection module  810  outputs a thesaurus entry  1204  for the word “bear,” which includes an indication  1206  of the type of reference work being utilized. 
     In this instance, the module  810  has additionally determined that the eBook  502  is associated with the genre of “business.” The module  810  may make this determination using any of the techniques described above, such as a by referencing a prior categorization of the eBook  502 , by analyzing key words of the eBook  502 , or the like. After making this determination, the reference entry selection module  810  outputs a business-related thesaurus entry  1204 , rather than a standard thesaurus entry. As such, the entry  1204  provides business-based synonyms for the term “bear,” such as pessimist, cynic, and defeatist. In addition, the entry  1204  includes an indication  1208  that this entry  1204  corresponds to a “business” use of the term. 
       FIG. 13  illustrates another example user interface rendered by the device  800  after the user has provided additional force on the touch-sensitive display  902 . Here, the touch-input controller  808  measures an amount of force  1302  provided by the additional input and provides this information to the reference entry selection module  810 . In response, the module  810  selects a reference work entry to output on the device  800 . In this instance, the module  810  again outputs a thesaurus entry  1304  (as shown by indication  1306 ). This thesaurus entry, however, is associated with a standard use of the term “bear” (as shown by indication  1308 ) and, as such, this entry includes synonyms such as carry, convey, and deliver. 
     As such,  FIGS. 12-13  illustrate that the user is able to toggle through multiple different context-sensitive reference work entries by providing varying amounts of force on the touch-sensitive display. In combination with the techniques described above with reference to context-sensitive reference works, a user is able to view an initial reference work entry that has been determined to most likely relate to the illustrated eBook, while providing the user the ability to toggle through multiple other entries. For instance, the techniques may surface a business-related thesaurus entry for a business-related book, while allowing the user to toggle through other thesaurus entries for a same word by applying an increased or decreased force to the display  902 . 
       FIG. 14  is a flow diagram showing a process  1400  of selecting which of multiple reference work entries to output based on an amount of measured force associated with a selection. This process (as well as the processes described below) is illustrated as a logical flow graph, each operation of which represents a sequence of operations that can be implemented in hardware, software, or a combination thereof. In the context of software, the operations represent computer-executable instructions stored on one or more computer-readable storage media that, when executed by one or more processors, perform the recited operations. Generally, computer-executable instructions include routines, programs, objects, components, data structures, and the like that perform particular functions or implement particular abstract data types. While this process illustrates one example order in which the operations of the process may occur, the example order is not intended to be construed as a limitation, and any number of the described operations can be combined in any order and/or in parallel to implement the process. 
     For discussion purposes, the process  1400  is described with reference to the device  800  of  FIG. 8 , although other devices and architectures may implement this process. 
     At operation  1402 , the device  800  detects an initial selection on a touch sensor and measures a force of the selection. For instance, a user of the device  800  may provide a touch input onto the touch-sensitive display of the device via a finger, stylus, or the like. This initial selection may select a particular portion of a content item, such as a word or phrase, a location on a map, a portion of an image, or any other portion of any type of content item. 
     At operation  1404 , the device  800  causes display of a first reference work entry at least partly in response to detecting the initial selection. For instance, the device  800  may display the first reference work entry on the touch-sensitive display of the device, on another display of the device, or on another display of a different device. Further, in some instances, the device  800  selects the first reference work entry based at least in part on the measured force of the initial selection. In other instances, meanwhile, the device  800  selects the first reference work entry regardless of an amount of force. In these latter instances, the measured force of the initial selection may act as a baseline for future touch inputs. 
     In each of these instances, the displayed first reference work entry may also be based on a location of the initial selection on the touch sensor. For instance, if a user provides the touch input on a portion of a touch-sensitive display displaying the word “mammal,” the device may output a reference work entry (e.g., a dictionary entry, an encyclopedia entry, etc.) associated with the word “mammal.” 
     At operation  1406 , the touch sensor of the device detects a force that is greater or lesser than the measured force of the initial selection. For instance, the user may have applied more force via her finger or a stylus, with or without removing her finger or stylus from touch sensor after making the initial selection. 
     At operation  1408  and in response to detecting the greater or lesser force, the device  800  causes display of a second, different reference work entry. Again, the device may display this entry on any display, such as on the touch-sensitive display of the device  800 . Further, this entry may be selected based on an amount of force of the selection and/or based on a difference in force between the initial selection and the greater/lesser force. This second, displayed entry may also be based on the portion of the content item that the user selects. In the example above, for instance, the device  800  may output a thesaurus entry for the word “mammal” in response to the user providing a greater amount of force at the location of the display displaying this word. 
       FIG. 15  illustrates yet another example user interface rendered by the device  800  of  FIG. 8  after a user has made a selection of a word on the touch-sensitive display  902  of the device  800 . As illustrated, the device  800  currently outputs the eBook  904  and the user provides a first input  1502  in the form of a touch on the touch-sensitive display  902 . In response, the device  800  outputs a reference work entry associated with the selected word. In the illustrated example, the device  800  again displays a dictionary entry  908  for the selected word “mammal.” 
       FIG. 16  illustrates an example user interface rendered by the device  800  after the user provides an additional input  1602 . This additional input may comprise additional force on the touch-sensitive display, a touch on the display that is coincident with the initial touch input, activation of a key on a keypad of the device  800 , an oral command spoken by the user and captured by a microphone of the device  800 , or any other type of input. 
     In response to the additional input  1602 , the device  800  outputs a second, different reference work entry  1004 . The device  800  may select this entry  1004  based on actual contents of the additional input  1602 , or the device  800  may select this entry  1004  based on the entry  1004  being “next in line” for display. 
     In either instance,  FIGS. 15-16  illustrate that a user of the device  800  is able to toggle through multiple reference work entries associated with a portion of a content item by providing a touch input and, thereafter, providing other preconfigured inputs. For instance, a user of the device may view a dictionary entry of a word by providing an initial touch input on the touch-sensitive display of the device. Thereafter, the user may toggle through multiple other reference work entries associated with the word by providing a second, coincident touch on the display. As such, the user could view a thesaurus entry by maintaining contact with her finger on the display and providing a first tap, an encyclopedia entry by providing a second tap, search engine results by providing a third tap, and so forth. 
     Conversely, the user could toggle through multiple different reference work entries by providing a touch input and then selecting a particular button on a keypad of the device. For instance, after providing a touch input, the user could select the “T” on the keypad to view the thesaurus entry for the word, the “E” on the keypad to view the encyclopedia entry of the word, and so forth. Conversely, the user may select a single button that toggles through these reference work entries in a preconfigured order. 
     In yet another example, the user could toggle through multiple different reference work entries by providing a touch input and then providing an oral command. For instance, the user could say aloud “thesaurus,” “encyclopedia,” “map,” and so forth. In response to the microphone of the device capturing the command, the device  800  may process this request and output the requested reference work entry. Conversely, the user may provide a single command (e.g., “next”) that, when received, causes the device to toggle through the reference work entries in a preconfigured order. 
       FIG. 17  is a flow diagram showing a process  1700  of outputting a first reference work entry in response to receiving a touch selection on a display and, thereafter, outputting a second, different reference work entry after receiving an additional input. 
     At operation  1702 , the device  800  receives a first user input on a touch-sensitive display  902  of the device  800 . For instance, the user may select a particular portion of a content item that the device outputs, such as a particular word or phrase of an eBook. 
     At operation  1704 , the device causes display of a first reference work entry associated with the selected portion of the content item. For instance, if the user selects the word “mammal,” the device  800  may display a dictionary entry or other reference work entry for this word. Conversely, if the user selects the word “Los Angeles,” the device  800  may display the location of this city on a map. 
     At operation  1706 , user provides and the device receives a second user input, which may or may not be coincident with the first input provided on the touch-sensitive display. For instance, the user may provide additional force on the display, may provide an additional point of contact or touch on the display, may activate a button on a keypad of the device, may orally speak a command, and so forth. 
     At operation  1708 , in response to receiving the second input the device  800  causes display of a second, different reference work entry. In some instances, this reference work entry is also associated with the initially selected portion of the content item. For instance, the device  800  may display a thesaurus entry for a selected word after displaying a dictionary entry for the word at the operation  1704 . 
       FIG. 18  illustrates an example user interface rendered by the device  800  of  FIG. 8  after a user has made a selection of a word on the touch-sensitive display  902  of the device  800 . In this example, the device  800  measures a force of the selection and determines whether to output a particular reference work entry in response to the selection, or whether to enable the user of the device  800  to select a reference work entry for output. For instance, the device  800  may determine whether a provided force is greater or less than a threshold force and, in response to this determination, may output the particular reference work entry or may enable the user to make the selection. 
       FIG. 18 , for instance, illustrates that the device  800  outputs a reference work entry (e.g., the dictionary entry  908 ) after determining that an amount of force  1802  of this selection is less than a threshold force. This threshold force may be configurable by a user of the device  800  in some instances. 
       FIG. 19 , meanwhile, illustrates an example user interface rendered by the device  800  after the device determines that an amount of force of this selection is greater than the threshold force. Here, the device  800  enables the user to select a reference work entry to output, each of which may be associated with the word “mammal.” In this example, the device  800  displays a menu  1902  with selectable icons, such as “dictionary entry,” “thesaurus entry,” and the like. With the menu  1902 , the user may select one of the icons to cause the device  800  to display the corresponding reference work entry. For instance, the user may select “encyclopedia entry” to view an encyclopedia entry for the word “mammal.” 
       FIGS. 18-19  thus illustrate that the device  800  may determine whether to output an entry or whether to enable a user to select an entry based on an amount of force of a user&#39;s selection. While these figures illustrate that the device enables user selection in response to detecting a force that is greater than a threshold force, in other instances the device may operate in an opposite manner. That is, the device  800  may enable the user to select a reference work entry in response to detecting a force that is less than a threshold force. Similarly, in these instances, the device  800  may output a particular reference work entry in response to detecting a force that is greater than the threshold force. 
     Furthermore, while  FIG. 19  illustrates one example manner that the user may select a reference work entry for output, the device  800  may enable this selection in a number of other ways. For instance, the device  800  may allow the user to orally state which reference work entry to output (e.g., “thesaurus”) or may allow the user to make this selection in any other manner. 
     These techniques may also operate in conjunction with the techniques for toggling through the multiple reference work entries, described above. For instance, the device may output a first entry in response to a first amount of force, a second entry in response to a second, greater amount of a force, and the selectable menu  1902  in response to a third, even greater amount of force. 
       FIG. 20  is a flow diagram showing a process  2000  of determining whether to output a reference work entry or whether to allow a user to select which reference work entry to output based on an amount of force of a selection. The device  800  and/or a component in communication with the device  800  may perform this process in some instances. 
     At operation  2002 , the device detects a selection on a touch-sensitive display of the device. For instance, the device may detect the user providing a touch input via her finger, a stylus, or the like. This selection may be associated with a particular portion of a content item being rendered by the device, such as a particular word or phrase of an eBook. 
     At operation  2004 , the device measures an amount of a force of the selection. At operation  2006 , the device then determines whether the measured amount of force is greater than or less than a preconfigured threshold value. In response to determining that the measured force is less than the threshold value, the device causes display of a reference work entry on the display at operation  2008 . Conversely, in response to determining that the measured amount of force is greater than the threshold amount of force, the device  800  enables the user select an entry at operation  2010 . For instance, the device  800  may output the selectable menu  1902  or may otherwise allow the user to select which reference work entry to display on the device. 
     Surfacing Content Based on Touch Gestures 
     Example eBook Reader Device 
       FIG. 21  is a block diagram of selected modules of an eBook reader device  2100  that may implement a touch-sensitive display and that is capable of outputting different content based on an amount of force applied to the touch-sensitive display. The illustrated eBook reader device  2100  may include several similar or identical components as the eBook reader devices  104 ( 1 ) and  800  described above. 
     In this example, the eBook reader device  2100  is a dedicated, handheld eBook reader device, although other electronic devices may implement these techniques and, hence, may include some of the functionality described herein. For instance, mobile telephones, tablet computers, laptop computers, desktop computers, personal media players, portable digital assistants (PDAs), kiosks, or any other type of electronic device may implement the components and techniques described below. 
     In a basic configuration, the example eBook reader device  2100  includes one or more processing units  2102  and memory  2104 . In addition, the eBook reader device  2100  may include the touch sensor  806  that enables a user of the device to operate the device via touch inputs. In some instances, the touch sensor  806  and the display  220  are integral to provide a touch-sensitive display that displays content items (e.g., eBooks) and allows users to navigate the content items via touch inputs on the display. 
     The memory  2104  may be used to store any number of functional components that are executable on the processing unit(s)  2102 , as well as data and content items that are rendered by the eBook reader device  2100 . Thus, the memory  2104  may store an operating system and an eBook storage database to store the one or more content items  206  described above, such as eBooks, audio books, songs, videos, still images, and the like. 
     A content presentation application  210  renders the content items  206 . The content presentation application  210  may be implemented as various applications depending upon the content items. For instance, the application  210  may be an electronic book reader application for rending electronic books, an audio player for playing audio books or songs, a video player for playing video, and so forth. 
     The memory  2104  may also store user credentials  212 . The credentials  212  may be device specific (set during manufacturing) or provided as part of a registration process for a service. The credentials may be used to ensure compliance with DRM aspects of rendering the content items  206 . 
     The memory  2104  also stores (persistently or temporarily) one or more reference works  214 , such as one or more dictionaries, thesauruses, encyclopedias, atlases, gazetteers, and the like. In some instances, the memory  204  stores multiple categories of a particular kind of reference work as described above. The memory  2104  may also include the interface module  208  that, as described above, provides for user operation of the device  2100 . One feature of the interface module  208  allows a user to request to receive information (e.g., from a reference work, from the Web, etc.) regarding a word, phrase, or topic found within one of the content items  206 . For instance, the interface module  208  may allow the user to request a definition of a word from a dictionary, synonyms from a thesaurus, a map from an atlas, search results from the Web, and the like. 
     The interface module  208  may facilitate textual entry of request (e.g., via a cursor, controller, keyboard, etc.), audible entry of the request (e.g., via a microphone), or entry of the request in any other manner. 
     The memory  2104  also stores the touch-input controller  808  to detect touch inputs received via the touch sensor  806  and, in some instances, to measure of a force of the touches. In some instances, the touch-input controller  808  is configured to detect multiple touches on the touch sensor  806  as well as to measure an amount of force of each of the touches. 
     The eBook reader device  2100  also stores a term aggregation module  2106  and a search refinement module  2108 . The term aggregation module  2106  is executable on the processing unit(s) to aggregate instances of a selected term and output one or more of these instances, such as on the display  220 . For instance, in response to a predefined user gesture, the module  2106  may aggregate or otherwise determine each instance of a selected term within an eBook that the device  2100  currently renders, within other eBooks stored on the device  2100 , and/or within available eBooks generally. The module  106  may then output a visual menu that indicates these other instances of the selected term. 
     In one specific example, the user of the device  2100  may select a particular word in an illustrated eBook with a particular amount of force. In response to this selection, the device  2100  may output information about the selected term. For instance, the device  2100  may illustrate a pop-up menu showing an entry associated with the selected word from one of the reference works  214 , such as a dictionary entry. Thereafter, the user may provide a greater or lesser amount of force to the selected word on the display  220  and, in response, the touch-input controller  808  may provide a notification of this greater or lesser force to the term aggregation module  2106 . In response to this notification, the term aggregation module  2106  may output other instances of the selected word within the illustrated eBook, as described in detail below. Additionally or alternatively, the term aggregation module  2106  may, in response to the greater or lesser force, output other instances of the selected word within other eBooks stored on the device  2100  and/or other eBooks that are not stored on the device  2100 . While a few example configurations have been described, multiple other configurations may also be implemented. 
       FIG. 21  further illustrates that the memory  2104  may store a search refinement module  2108 . The search refinement module  2108  is executable on the processing unit(s)  2102  to refine a user&#39;s search based on varying magnitudes of force associated with a selection of the user. For instance, a user may request that the device  2100  perform a local or remote search by selecting a particular word of an illustrated eBook to use as a query for the search. This search may comprise a search of eBooks or other content items stored on the device, a search of results available on the Web, or the like. 
     After the device  2100  surfaces the results, the user may thereafter provide a selection having a greater or lesser amount of force than the initial selection. In response, the search refinement module  2108  may refine the search by, for instance, expanding or narrowing the search. For instance, the search refinement module  2108  may expand a search in response to the user providing a lesser amount of force on the touch-sensitive display, and/or may narrow a search in response to the user providing a greater amount of force, each of which are described in more detail below. 
     The eBook reader device  2100  may further be equipped with various input/output (I/O) components  222 , similar to the devices  104 ( 1 ) and  800  described above. Such components may include various user interface controls (e.g., buttons, a joystick, a keyboard, etc.), audio speakers, connection ports, and so forth. In addition, a network interface  224  supports both wired and wireless connection to various networks, such as cellular networks, radio, WiFi networks, short range networks (e.g., Bluetooth), IR, and so forth. The network interface  224  may allow a user of the device  800  to download content items from the content item service  106 . 
     The eBook reader device  2100  also includes a battery and power control unit  226 . The battery and power control unit operatively controls an amount of power, or electrical energy, consumed by the eBook reader device. Actively controlling the amount of power consumed by the reader device may achieve more efficient use of electrical energy stored by the battery. 
     Example User Interfaces and Processes for Surfacing Other Instances of a Selected Term 
       FIG. 22  illustrates an example user interface rendered by the device  2100  of  FIG. 21 . As illustrated, the device includes the touch-sensitive display  902  that renders an eBook  2202 , which in this example comprises the play “Hamlet” by William Shakespeare. During rendering of the eBook  904 , a user makes a selection of a word (“Ophelia”) on the touch-sensitive display  902 , as illustrated by the highlight  126 . In response, the touch-input controller  808  of the device  2100  measures an amount of force  2204  of the selection. In addition, the device  2100  may output information regarding the selected word. In one example, the device  2100  may output a reference work entry associated with the selected word. Here, the device  2100  outputs an entry  2206  describing the role of the selected character, Ophelia, within the illustrated eBook  2202 . The entry  2206  also includes an icon  2208  (entitled “More”) that, when selected, expands or otherwise provides additional information from the entry  2206 . 
     In some instances, the touch-input controller  808  may provide an indication of the measured amount of force to the reference work selection entry shown in  FIG. 8 , which may map the detected amount of force to a particular type of reference work entry to output. For instance, the module  810  may output a first type of reference work entry for a touch-input having a measured force within a first range, a second type of reference work entry for a touch-input having a measured force within a second range, and so forth. 
     In other instances, meanwhile, the controller  808  may measure the amount of force  2204  of the initial touch and may use this amount as a baseline for future touches. For instance, the device  2100  may select and output a first type of information (e.g., entry  2206 , Web search results for “Ophelia,” etc.) in response to detecting a first touch, regardless of the amount of force of the touch. Thereafter, the device  2100  may provide different outputs in response to detecting touches having greater or lesser forces than the initial “baseline” touch, as described immediately below. 
       FIG. 23  illustrates an example user interface rendered by the device  2100  after the user has increased the amount of force on the selected word. As illustrated, the user now selects the word “Ophelia” with an amount of force  2302  that is greater than the amount of force  2204 . The user may or may not have maintained contact with the touch-sensitive display  902  between the applications of these two forces. In response to the second input of the user, the touch-input controller  808  has detected the greater amount of force  2302  and has provided this information to the term aggregation module  2106 . In response, the module  2106  may determine whether the increased force is greater than a threshold and, if so, may output information that is different than the entry  2206  of  FIG. 22 . 
     For instance, the module  2106  may output other instances of the selected term “Ophelia,” either within the eBook  2202 , within other eBooks stored on the device  2100 , or within other content items. Here, the module  2106  has output a menu  2304  of other instances of the term “Ophelia” within the illustrated eBook  2202 , Hamlet. In some instances, each listing of the instance of the selected term may be selectable by the user, such that a selection of that instance may cause the device  2100  to navigate the user to that location in the eBook  2202  or may cause an overlay of that location in the eBook  2202 . 
     In the illustrated example, the menu  2304  displays other mentions or instances of the term “Ophelia” starting with the beginning of the play. Conversely, the menu  2304  could depict instances of the selected term that are nearest the instance of the selected term or may surface these other instances in any other matter. In either instance, the menu  2304  may include the icon  2208  that, when selected, causes the device  2100  to illustrate more instances of “Ophelia” and their corresponding locations. 
     While  FIG. 23  illustrates that the device  2100  outputs the menu  2304  in response to detecting the amount of force  2302  on the location of the display  902  associated with the word “Ophelia,” other implementations may output this menu  2304  based detecting a force at another location the display  902 . 
       FIG. 24  illustrates yet another example user interface rendered by the device  2100  after the user has yet again provided an input having an increased amount of force  2402  on the selected word “Ophelia.” The touch-input controller  808  measures the increased force  2402  and provides this information to the term aggregation module  2106 . In response, the module  2106  outputs still different information regarding the selected term. In the illustrated example, the module  2106  outputs a menu  2404  of other mentions of the term “Ophelia” within other eBooks or content items stored on or accessible by the device  2100  of the user. That is, the menu  2404  may include indications of other works that the user of the device  2100  has previously purchased and/or obtained (e.g., downloaded). 
     Here, the menu  204  indicates that the term Ophelia shows up in three eBooks to which the device has access to. With use of the menu  2404 , the user may select different ones of the listings, which in turn may cause the device to display the selected eBook, potentially at the first use of the term “Ophelia” within that book. While  FIG. 24  illustrates other mentions or instances of the selected term within items to which the device user has access to, in other implementations the menu  2404  may include other items that the user currently does not have access to. Further, the menu could provide icons that, when selected, initiate a request for a sample of an item or a request to obtain (e.g., purchase) the item. As such, the user may be able to obtain other items that are associated with or otherwise reference the term “Ophelia,” if the user so desires. 
       FIG. 25  illustrates an example user interface rendered by the device  2100  after the user has yet again increased an amount of force  2502  on the selected word. Here, the device  2100  outputs search results  2504  associated with a query comprising the selected word (“Ophelia”) based on this even greater amount of force  2502 . As illustrated, the search results may comprise Web results provided by a search engine. 
     With use of the described techniques, the user of the device  2100  is able to toggle through different information associated with a particular term (e.g., word or phrase) by altering the amount of force applied to the touch-sensitive display  902 . Specifically, the user may request to view other instances of a selected term by providing a greater or lesser amount of force to the display  902  than an initial selection. Furthermore, while  FIG. 22-25  illustrate an example navigation path associated with four different levels of force, other implementations may employ any other combination of information associated with the selected term. Furthermore, both the navigation path (i.e., the surfaced information associated with the selected term) and the force thresholds for navigating this path may be configured by the user in some implementations. 
       FIG. 26  is a flow diagram showing a process  2600  of causing display of other instances of a selected term based on a force associated with a selection. This process (as well as the processes described below) is illustrated as a logical flow graph, each operation of which represents a sequence of operations that can be implemented in hardware, software, or a combination thereof. In the context of software, the operations represent computer-executable instructions stored on one or more computer-readable storage media that, when executed by one or more processors, perform the recited operations. Generally, computer-executable instructions include routines, programs, objects, components, data structures, and the like that perform particular functions or implement particular abstract data types. While this process illustrates one example order in which the operations of the process may occur, the example order is not intended to be construed as a limitation, and any number of the described operations can be combined in any order and/or in parallel to implement the process. 
     For discussion purposes, the process  2600  is described with reference to the device  2100  of  FIG. 21 , although other devices and architectures may implement this process. 
     At operation  2602 , the device  2100  detects an initial selection on a touch sensor and measures a force of the selection. For instance, a user of the device  2100  may provide a touch input onto the touch-sensitive display of the device via a finger, stylus, or the like. This initial selection may select a particular portion of a content item, such as a term (e.g., word or phrase), a location on a map, a portion of an image, or any other portion of any type of content item. In this example, the user selects a particular term. 
     At operation  2604 , the device  2100  causes display of information associated with the selected term at least partly in response to detecting the initial selection. For instance, the device  2100  may display a reference work entry or other information associated with the term on the touch-sensitive display of the device, on another display of the device, or on another display of a different device. Further, in some instances, the device  2100  selects the information (e.g., the reference work entry) based at least in part on the measured force of the initial selection. In other instances, meanwhile, the device  2100  selects the information to surface regardless of an amount of force. In these latter instances, the measured force of the initial selection may act as a baseline for future touch inputs. 
     At operation  2606 , the touch sensor of the device detects a force that is greater or lesser than the measured force of the initial selection. For instance, the user may have applied more force via her finger or a stylus, with or without removing her finger or stylus from touch sensor after making the initial selection. 
     At operation  2608 , and in response to detecting the greater or lesser force, the device  2100  causes display of one or more other instances of the selected term. Again, the device may display this entry on any display, such as on the touch-sensitive display of the device  2100 . Further, the other instances of the selected term may comprise other instance of the term within the illustrated content item, within other content items associated with the device  2100 , or within other content items generally. In some implementations, the device  2100  determines which of these “other instances” to surface based on an amount of force of the selection and/or based on a difference in force between the initial selection and the greater/lesser force. For instance, a first greater amount of force may result in the device  2100  surfacing other instances of the selected term within the currently illustrated eBook, while a second, greater amount of force may result in the device  2100  surfacing other instances of the selected term within the other eBooks stored on or accessible by the device. Other examples are also possible. 
       FIG. 27  illustrates an example user interface rendered by the device  2100  after a user has made a selection of a word within the eBook  2200  being rendered on the touch-sensitive display  902  of the device  2100 . Here, the user provides a touch of a certain threshold amount of force  2702  on the display, which the touch-input controller  808  detects. In response, the device  2100  outputs a menu  2704  requesting that the user select whether to view previous or subsequent instances of the selected word within the illustrated content item. 
     In this example, the menu comprises a left-facing arrow  2706  that, when selected, causes the device to render instances of “Ophelia” within Hamlet that occur prior to a current reading location of the user. The menu  2704  also includes a right-facing arrow  2708  that, when selected, causes the device to render instances of “Ophelia” within Hamlet that occur subsequent to a current reading location of the user. While  FIG. 27  illustrates arrows, the menu  2704  may include any other icons to allow the user to select whether to surface previous instances of a selected term, subsequent instances, or both. 
       FIG. 28  illustrates an example user interface rendered by the device  2100  while a user makes a gesture  2802  that both selects a word within a content item and requests to view subsequent instances of the selected word within the illustrated content item. Here, the gesture  2802  comprises the user pressing on a particular term of the eBook  2202  (“Ophelia”) with a certain amount of force  2702 , while also swiping her finger to the right. In this example, the device  2100  interprets this gesture to mean that the user wishes to view instances of “Ophelia” within Hamlet that occur subsequent to a current reading location of the user within the eBook. 
       FIG. 29  illustrates an example user interface rendered by the device  2100  after the user makes the gesture  2802  in  FIG. 28 . As illustrated, in response to the gesture  2802  the device  2100  surfaces a menu  2902  that indicates that the illustrated eBook  2202  does not contain any subsequent instances of the selected term. In addition, the menu  2902  includes a link  2904  that, when selected, allows the user to view previous instances of the term “Ophelia” within the illustrated eBook  2202 . 
       FIG. 30  is a flow diagram showing a process  300  of causing display of information associated with a portion of a content item in response to receiving a touch selection of the portion on a display and, thereafter, outputting other instances of the portion after receiving an additional input. The process  3000  includes, at  3002 , receiving a first user input selecting a portion of a content item being output on a touch-sensitive display. For instance, the user may select a particular term of an eBook, a geographical location on a map, a character in an illustration, or any other defined portion of a content item. In response, at  3004  the device causes display of information associated with the selected portion. For instance, the device may cause display of a reference work entry associated with a selected word or phrase, a biography of a selected character or person, a location on a map of a selected geographical location, or any information associated with the selected portion. 
     At  3006 , the device receives a second user input requesting to view other instances of the selection portion of the content item within the content item. For instance, the user may provide a greater or lesser amount of force on the selected portion, as discussed. Additionally or alternatively, the user may select a particular button on the keypad of the device, may state an aural command, may provide a second and coincident touch on the display, or the like. In response, at  3008  the device may cause display of other instances of the selected portion within the content item. For instance, the device may indicate other textual or graphical locations where the selected portion occurs within the content item. This may include other textual mentions of the portion, other instances of the selected portion within an image, photograph, or map, or any other type of instances of the selected portion of the item. 
     Example User Interfaces and Processes for Refining Search Results 
       FIG. 31  illustrates an example user interface rendered by the device  2100  after the user selects a word, via a touch input  3102 , within the illustrated eBook  2202 . In response to the selection, the device  2100  may form a query comprising the select word and may perform a local and/or remote search based on the query. For instance, the device  2100  may pass the query to a search engine to run a Web search on the selected term “Ophelia” and may thereafter output search results  3104 . While the device may conduct a Web search with use of the selected term, the device  2100  may alternatively conduct a local search of the device  2100  and/or a search of one or more other defined devices or domains. 
       FIG. 32  illustrates an example user interface rendered by the device  2100  after the user provides a greater amount of force  3202  to the selected word. Here, the touch-input controller  808  detects this greater amount of force  3202  and passes an indication of the increased force to the search refinement module  2108 . In response, the search refinement module  2108  may refine (e.g., narrow) the search results  3104 . For instance, the search refinement module  2108  may form another, more narrow query in response to receiving this indication and may thereafter display search results  3204  associated with this narrower query. 
     In some instances, the narrowed query comprises the selected term and at least one other term associated with the content item being output by the touch-sensitive display. For instance, the additional term may comprise at least a portion of a title of the content item, an author of the content item, a topic of the content item, a categorization of the content item, or any other information associated with the content item, the exact selection of which may or may not be configurable by the user. In the illustrated example, the module  2108  conducts a search for a query comprising the selected term (“Ophelia”) and a title of the illustrated eBook  2202  from which the term was selected (“Hamlet”). As such, the device  2100  outputs search results  3204  for the query “Ophelia Hamlet.” 
     Additionally or alternatively, the search refinement module  2108  may broaden or narrow displayed search results based on crowd-sourcing—that is, with reference to the navigation of users having previously navigated search results associated with the illustrated search. In some instances, the module  2108  may reference previous navigation of users that have conducted a search from within a particular content item, such as the illustrated play “Hamlet.” For instance, if a large number of users selected a certain set of items in search results when conducting the search “Ophelia” within Hamlet (or within related works), then the module  2108  may highlight these popular items in response to receiving a user request to narrow a search for “Ophelia” within the eBook  2202  (Hamlet). 
     In some instances, the user may broaden a search by lessening the amount of force provided on the touch-sensitive display  902 . For instance, if the user were to lessen the amount of force from the amount  3202  to the amount  3102 , then the search refinement module  2108  may broaden the search by forming a query “Ophelia” rather than “Ophelia Hamlet.” In response, the device  2100  may display the search results  3104 . 
       FIG. 33  is a flow diagram showing a process  3300  of refining search results on a touch-sensitive display based on the device detecting a greater or lesser amount of force on a selected term. For discussion purposes, the process  3300  is described with reference to the device  2100  of  FIG. 21 , although other devices and architectures may implement this process. 
     At operation  3302 , the device  2100  detects an initial selection on a touch sensor and measures a force of the selection. For instance, a user of the device  2100  may provide a touch input onto the touch-sensitive display of the device via a finger, stylus, or the like. This initial selection may select a particular portion of a content item, such as a term (e.g., word or phrase), a location on a map, a portion of an image, or any other portion of any type of content item. In this example, the user selects a particular term. 
     At operation  3304 , the device  2100  forms a query comprising (e.g., consisting of) the selected term and thereafter causes display of search results associated with this term. In some instance, the search results are local, remote, web-based, or any combination thereof. For example, the device may submit the formed query to a remote search engine in some examples. At operation  3306 , the touch sensor of the device detects a force that is greater or lesser than the measured force of the initial selection. For instance, the user may have applied more force via her finger or a stylus, with or without removing her finger or stylus from touch sensor after making the initial selection. 
     At operation  3308  and in response to detecting the greater or lesser force, the device  2100  refines the displayed search results. For instance, the search refinement module  2108  may form another query and may surface search results associated with this broader or narrower query. 
       FIG. 34  illustrates an example user interface rendered by the device  2100  while a user makes a gesture  3402  that both selects a word within the illustrated eBook  2202  and requests to narrow illustrated search results associated with the selected word. In this example, the user may have previously requested to view search results associated with the word “Ophelia” and, in response, the device  2100  illustrates corresponding search results  3104 . Thereafter, the user performs the gesture  3402 , which in this example comprises the user swiping downwards with reference to controls of the device  2100  or the orientation of the eBook  2202 . 
       FIG. 35  illustrates an example user interface rendered by the device  2100  after the user performs the gesture  3402 . As illustrated, the device has narrowed the search results in response to detecting the gesture. Specifically, the search refinement module  2108  has formed a query (“Ophelia Hamlet”) that is narrower than the previous query (“Hamlet”). In addition, the device  2100  now displays search results  3204  associated with the narrower query. 
       FIG. 36  illustrates an example user interface rendered by the device  2100  while a user makes a gesture  3602  that both selects a word within the illustrated eBook  2202  and requests to expand illustrated search results associated with the selected word. In this example, the device  2100  currently displays the search results  3204  discussed immediately above with reference to  FIG. 35 . In addition, in this example the gesture  3602  comprises the user performing an upwards swipe. 
       FIG. 37  illustrates an example user interface rendered by the device  2100  after the user performs the upward swipe gesture of  FIG. 36 . As illustrated, the device has expanded search results in response to detecting the gesture. Specifically, the search refinement module  2108  has surfaced search results  3104  associated with the query “Ophelia,” rather than the previously surfaced results associated with the narrower query “Ophelia Hamlet.” As such, the user has been able to quickly and efficiently narrow and/or broaden search results with use of predefined and intuitive gestures. While the foregoing figures have provided a few predefined gestures and corresponding directionality that may be suitable for refining search results, multiple other gestures and/or directions may be used in other implementations. 
       FIG. 38  is a flow diagram showing a process  3800  for refining search results based at least in part on detecting a predefined gesture on a touch-sensitive display. At  3802 , the device  2100  detects an initial selection of a term in a content item, such as the eBook  2202 . In response, the device  2100  may form a query and may display search results associated with the query at  3804 . 
     At  3806 , the device  2100  may detect a predefined gesture on the touch-sensitive display  902  of the device  902  during the display of the search results. This predefined gesture may comprise a user swipe on the touch-sensitive display in a predefined direction, such as upwards to broaden the search or downwards to narrow the search. Additionally or alternatively, the predefined user gesture may comprise additional or less force on the touch-sensitive display, or any other predefined user gesture. 
     At  3808 , the search refinement module  2108  of the device  2100  may refine the search results on the display based at least in part on detecting the predefined gesture. For instance, the module  2108  may expand the search results or narrow the search results, depending upon the detected gesture made by the user. 
     CONCLUSION 
     Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described. Rather, the specific features and acts are disclosed as exemplary forms of implementing the claims.