Quotation marks or inverted commas (informally known as quotes and speech marks) are punctuation marks used in pairs to mark a section of text as speech, a quotation, a phrase, or an unusual word. They are used in groups of 2, as a pair of opening and closing marks. They are used in either of two forms:  or .

Depending on the typeface, the opening and closing quotation marks may be identical in form (called “vertical” or “straight” or “typewriter” quotation marks), or they may be distinctly left-handed and right-handed (“typographic” or, colloquially, “curly” quotation marks).  The closing single quotation mark is identical or similar in form to the apostrophe, and similar to the prime symbol.  However, these three characters have quite different purposes.  See also: ditto mark.

Usage

Quotations and speech 
Quotation marks show that part of the text is either a person speaking or a quotation. Double quotation marks are used as a rule in the United States, while both single and double quotation marks are used in the United Kingdom and other commonwealth countries. A publisher’s or author’s style can be considered as more important than national preferences. However, the style of opening and closing quotation marks must be matched:

 ‘Good morning, Frank,’ said HAL.
 “Good morning, Frank,” said HAL.

For speech within speech, the other mark is used for inner quotations, within a quotation:

 Frank reported that ‘HAL said, “Good morning, Dave,”’.
 Frank reported that “HAL said, ‘Good morning, Dave,’”.

Sometimes, quotations are nested in more than two levels. Nesting levels up to five can be found in some translations of the Bible. In these cases, questions arise about the form (and names) of the quotation marks to be used. The most common way is to simply alternate between the two forms, thus:

 “…‘…“…‘ …   … ’……’…”

If such a passage is further quoted in another publication, then all of their forms have to be shifted over by one level.

In most cases, quotations which span multiple paragraphs should be set as block quotations, and thus do not require quotation marks. Quotation marks are used for multiple-paragraph quotations in some cases, especially in narratives. The convention in English is to put an opening quotation mark at the first and each subsequent paragraph, but use a closing quotation mark only for the final paragraph of the quotation, as in the following example from the book Pride and Prejudice:

As noted below, in some older texts, the quotation mark is repeated every line, rather than every paragraph. The Spanish convention uses closing quotation marks at the beginning of all subsequent paragraphs beyond the first.

When quoted text is interrupted, such as with the phrase he said, a closing quotation mark is used before the interruption, and an opening quotation mark after. Commas are also often used before and after the interruption, more often for quotations of speech than for quotations of text:

 “HAL,” noted Frank, “said that everything was going extremely well.”

It is incorrect to use quotation marks for paraphrased speech.  This is because a paraphrase is an indirect quote, and in the course of any composition, it is important to document when one is using a quotation versus when one is using a paraphrased idea.

If HAL says: “All systems are functional,” then:

 Incorrect: HAL said that “Everything was going extremely well.”
 Correct: HAL said that everything was going extremely well.

However, another convention when quoting text in the body of a paragraph or sentence—for example, in an essay—is to recognize double quotation marks as marking an exact quotation, and single quotation marks as marking a paraphrased quotation or a quotation where grammar, pronouns, or plurality have been changed in order to fit the sentence containing the quotation (see reported speech).

Irony 
Another common use of quotation marks is to indicate or call attention to ironic or mis-used words:

 He shared his “wisdom” with me.
 The lunch lady plopped a glob of “food” onto my tray.
 She attempted to use her “strength” to lift the weight.

Quotes indicating irony, or other special use, are sometimes called scare quotes. They are sometimes gestured in oral speech using air quotes.

Signaling unusual usage 

Quotation marks are also used to indicate that the writer realizes that a word is not being used in its current commonly accepted sense.

 Crystals somehow “know” which shape to grow into.

In addition to conveying a neutral attitude and to call attention to a neologism, or slang, or special terminology (also known as jargon), quoting can also indicate words or phrases that are descriptive but unusual, colloquial, folksy, startling, humorous, metaphoric, or contain a pun:
	 
Dawkins’s concept of a meme could be described as an “evolving idea”.
	 
People also use quotation marks in this way to:
 distance the writer from the terminology in question so as not to be associated with it. For example, to indicate that a quoted word is not official terminology, or that a quoted phrase presupposes things that the author does not necessarily agree with.
 indicate special terminology that should be identified for accuracy’s sake as someone else’s terminology, for example if a term (particularly a controversial term) pre-dates the writer or represents the views of someone else, perhaps without judgement (contrast this neutrally-distancing quoting to the negative use of scare quotes)

The Chicago Manual of Style (CMS), 15th edition acknowledges this type of use but cautions against overuse in section 7.58, “Quotation marks are often used to alert readers that a term is used in a nonstandard, ironic, or other special sense […] They imply ‘This is not my term,’ or ‘This is not how the term is usually applied.’ Like any such device, scare quotes lose their force and irritate readers if overused.”

Use–mention distinction 

Using either quotation marks or italics can emphasize that an instance of a word refers to the word itself, rather than its associated concept.

 Cheese is derived from milk.
 “Cheese” is derived from a word in Old English.
 Cheese has calcium, protein, and phosphorus.
 Cheese has three es in the spelling.

A three-way distinction is occasionally made between normal use of a word (no quotation marks), referring to the concept behind the word (single quotation marks), and the word itself (double quotation marks):

 When discussing ‘use’, use “use”.

The logic, for this form, derives from the need to distinguish use forms, coupled with the mandate to retain consistent notation for like use forms.  The switching between double and single quotes in nested citation quotes reveals the same literary device for reducing ambiguity.

Books about language often use italics for the word itself and single quotation marks for a gloss:

 The French word canif ‘pocketknife’ is borrowed from Old English cnif ‘knife’.

Titles of artistic works 
Quotation marks, rather than italics, are generally used for the titles of shorter works. Whether these are single or double is again a matter of style; however, many styles, especially for poetry, prefer the use of single quotation marks.
 Short fiction, poetry, etc.: Arthur C. Clarke’s “The Sentinel”
 Book chapters: The first chapter of 3001: The Final Odyssey is “Comet Cowboy”
 Articles in books, magazines, journals, etc.: “Extra-Terrestrial Relays”, Wireless World, October 1945
 Album tracks, singles, etc.: David Bowie’s “Space Oddity”

As a rule, a whole publication would be italicised, whereas the titles of minor works (such as poems or short stories inside the collection) would be written with quotation marks.
 Shakespeare’s Romeo and Juliet
 Dahl’s “Taste” in Completely Unexpected Tales

Nicknames and false titles 
Quotation marks can also offset a nickname embedded in an actual name, or a false or ironic title embedded in an actual title; for example, Nat “King” Cole, Miles “Tails” Prower, or John “Hannibal” Smith.

Emphasis (incorrect usage) 
Quotes are sometimes used incorrectly for emphasis in lieu of underlining or italics, most commonly on signs or placards. This usage can be confused with ironic or altered-usage quotation, sometimes with unintended humor. For example, For sale: “fresh” fish, “fresh” oysters, could be construed to imply that fresh is not used with its everyday meaning, or indeed to indicate that the fish or oysters are anything but fresh. And again, Cashiers’ desks open until noon for your “convenience” might mean that the convenience was for the bank employees, not the customers.

Typographical considerations

Punctuation 

With quotation marks that are next to other punctuation marks, there are two main systems.  They are called “American” and “British,” but some American writers and organizations use the British style and vice versa.  Both systems have the same rules for question marks, exclamation points, colons, and semicolons.  They have different rules for periods and commas.

In both systems, question marks and exclamation marks are placed inside or outside quoted material depending on whether they are for the whole sentence or just the quoted words, but colons and semicolons always go outside.

 Did he say, “Good morning, Dave”?
 No, he said, “Where are you, Dave?”
 There are three definitions of the word “gender”: colloquial, sociological, and linguistic.

In American style, commas and periods almost always go inside closing quotation marks. 
This style of punctuation is common in the U.S., Canada, and it is also used in the U.K. in fiction and journalism.

In British style, which is sometimes called logical punctuation, the rule is the same as for question marks and exclamation points: the comma or period goes outside if it is for the whole sentence but inside if it is for just the quoted words.  This is called “placement according to sense.”

Examples
When dealing with words-as-words, short-form works like the titles of songs, and sentence fragments, the two systems are different:

 “Carefree,” in general, means “free from care or anxiety.” (American practice)
 “Carefree”, in general, means “free from care or anxiety”. (British practice)
 Bruce Springsteen, nicknamed “The Boss,” performed “American Skin.” (American practice)
 Eric Clapton, nicknamed “God”, performed “Layla”. (British practice)

For quoting direct speech, American rules place periods and commas inside the quotation marks all the time.  In fiction, both styles are the same.  In non-fiction, British publishers may permit placing punctuation that is not part of the person’s speech inside the quotation marks but prefer that it be placed outside. According to the Cambridge Handbook for Editors, Copy-editors and Proofreaders, periods and commas that are part of the person’s speech are permitted inside the quotation marks regardless.

 “Today,” said Cinderella, “I feel free from care and anxiety.” (both major styles)
 “Today”, said former Prime Minister Tony Blair, “I feel free from care and anxiety.” (British non-fiction only)
 “I feel happy,” said Bjork, “carefree, and well.” (both major styles)

Many American style guides explicitly permit periods and commas outside the quotation marks when the presence of the punctuation mark inside the quotation marks will lead to ambiguity, such as when describing keyboard input:

 To use a long dash on Wikipedia, type in “&mdash;”.

In the first two sentences above, only one punctuation mark is used at the end of each. Regardless of its placement, only one end mark (?, !, or .) can end a sentence in American English. Only the period, however, cannot end a quoted sentence when it does not also end the enclosing sentence, except for literal text:

 “Hello, world,” she said.
 “Hello, world!” she exclaimed.
 “Is there anybody out there?” she asked into the void.
 “Goodnight, stars. Goodnight, moon,” she whispered.
 The name of the song was, he replied, “Moonlight,” which many already knew.
References: Chicago Manual of Style, 15th edition; Hart’s Rules for Compositors and Readers at the University Press, Oxford; Merriam-Webster’s Guide to Punctuation and Style, second edition.

Spacing 
In English, when a quotation follows other writing on a line of text, a space precedes the opening quotation mark unless the preceding symbol, such as a dash, requires that there be no space. When a quotation is followed by other writing on a line of text, a space follows the closing quotation mark unless it is immediately followed by other punctuation within the sentence, such as a colon or closing punctuation. (These exceptions are ignored by some Asian computer systems that systematically display quotation marks with the included spacing, as this spacing is part of the fixed-width characters.)

There is generally no space between an opening quotation mark and the following word, or a closing quotation mark and the preceding word. When a double quotation mark or a single quotation mark immediately follows the other, proper spacing for legibility requires that a non-breaking space be inserted.

 So Dave actually said, “He said, ‘Good morning’ ”?
 Yes, he did say, “He said, ‘Good morning.’ ”

Non-language related usage 
Straight quotation marks (or italicized straight quotation marks) are often used to approximate the prime and double prime. For example, when signifying feet and inches, arcminutes and arcseconds, or minutes and seconds, where the quotation mark symbolises the latter part of the pair. For instance, 5 feet and 6 inches is often written 5' 6", and 40 degrees, 20 arcminutes and 50 arcseconds is written 40° 20' 50". When available, however, the prime should be used instead (e. g., 5′ 6″, and 40° 20′ 50″). Prime and double prime are not present in most character sets, including ASCII and Latin-1, but are present in Unicode, as characters U+2032 (dec. 8242) and U+2033 (dec. 8243), and as HTML entities &prime; and &Prime;. Double quotation marks are also often used to represent the ditto mark.

Straight single and double quotation marks are used in most programming languages to delimit strings or literal characters. In some languages (e. g. Pascal) only one type is allowed, in some (e. g. C and its derivatives) both are used with different meanings and in others (e. g. Python) both are used interchangeably. In some languages, if it is desired to include the same quotation marks used to delimit a string inside the string, the quotation marks are doubled. For example, to represent the string eat 'hot' dogs in Pascal one uses 'eat ''hot'' dogs'.  Other languages use an escape character, often the backslash, as in 'eat \'hot\' dogs'.

Typing quotation marks on a computer keyboard

Standard English computer keyboard layouts inherited the single and double “straight” quotation marks from the typewriter (the single quotation mark also doubling as an apostrophe), and they do not include individual keys for left-handed and right-handed typographic quotation marks. However, most computer text-editing programs provide a “smart quotes” feature (see below) to automatically convert “straight” quote marks into typographic punctuation. Generally, this “smart quote” feature is enabled by default. Some websites do not allow typographic quotation marks or apostrophes in posts (one such example being YouTube). One can skirt these limitations, however, by using the HTML character codes or entities.

Smart quotes
To make typographic quotation marks easier to enter, publishing software often automatically converts typewriter quotation marks (and apostrophes) to typographic form during text entry (with or without the user being aware of it). This is known as the “smart quotes” feature. Quotation marks that are not automatically altered by computer programs are known as “dumb quotes”. Some implementations incorrectly produce an opening single quotation mark in places where an apostrophe is required, for example, in abbreviated years like ’08 for 2008.

History 
In the first centuries of typesetting, writers showed quoted speech by saying who was speaking. Some versions of the Bible still do it this way.  During the Renaissance, writers showed quoted speech by using a typeface different from the main body text, like we use italics today.  Long quotations were also set this way, at full size and full measure.

Quotation marks were first cut in metal type during the middle of the sixteenth century, printers were using them a lot by the seventeenth.  In some Baroque and Romantic-period books, quotation marks would be repeated at the beginning of every line of a long quotation.  When printers stopped doing this, they still kept the empty margin, which is where we get our modern practice of indenting before block quotation.

In Early Modern English, quotation marks were used only to denote pithy comments. Writers first began to use them for direct speech in 1714. By 1749, writers were using single quotation marks, or inverted commas, for direct speech.

Related pages
 Okina - an accent mark used in words from Hawaii
 ISO 8859-1 - document of the International Organization for Standardization
 Typewriter conventions

Notes

References 
 Bringhurst, Robert (2002). The Elements of Typographic Style, version 2.5. Vancouver, Hartley & Marks. .
 Butcher, Judith (1992). Copy-editing: The Cambridge Handbook for Editors, Authors and Publishers, third edition. pp 264–266. Cambridge University Press. .

Other websites
 Curling Quotes in HTML, SGML, and XML 
 Quotation marks in the Unicode Common Locale Data Repository
 ASCII and Unicode quotation marks – detailed discussion of the ASCII `backquote' problem
 The Gallery of “Misused” Quotation Marks
  The “Blog” of “Unnecessary” Quotation Marks
 Commonly confused characters
 Smart Quotes
 Quotation mark
 Quotation marks -Citizendium

Punctuation
Typography