Fingerspelling
Fingerspelling (sometimes known as dactylology) is the representation of the letters of a writing system, and sometimes numeral systems, using only the hands. There are many manual alphabets (also known as finger alphabets or hand alphabets) in use, past and present  especially in deaf education and, subsequently adopted as a distinct part of a number of sign languages around the world.
As with other forms of manual communication, fingerspelling can be comprehended visually or tactually. The simplest visual form of fingerspelling is tracing the shape of letters in the air, or tactually, tracing letters onto the palm. However, most manual alphabets use a unique hand sign to represent individual letters, distinguished by handshape and palm orientation, and sometimes movement, location and mouth patterns. The handshapes are often based on stylised representations of the shapes of the letters as they are written, but may be arbitrary signs, or a combination of iconic and arbitrary signs.
Manual alphabets exist for representing Latin, Cyrillic, Greek, Devanagari, Bengali, Arabic, Hebrew, Thai, Hangul, Kanji, Kana and Ge'ez scripts. Related manual systems are in use which phonetically represent sound, rather than the written form of a spoken language. These systems, sometimes called "Mouth Hand Systems" (MHS) include Cued Speech and a unique MHS developed in Denmark in 1903 by Georg Forchhammer.

# Fingerspelling in sign languages
Fingerspelling has been introduced into certain sign languages by educators, both deaf and hearing, and as such has some structural properties that are unlike the visually-motivated and multi-layered signs that are typical in deaf sign languages. In many ways fingerspelling serves as a bridge between the sign language and the spoken language that surrounds it.
Fingerspelling is used in different sign languages and registers for different purposes. It may used be to represent words which have no sign equivalent, or for emphasis, clarification, or when teaching or learning a sign language.  In American Sign Language (ASL), more lexical items are fingerspelled in casual conversation than in formal or narrative signing. Different sign language "speech communities" use fingerspelling to a greater or lesser degree. At the high end of the scale, fingerspelling makes up about 8.7% of casual signing in ASL, and 10% of casual signing in Auslan. The proportion is higher in older signers, suggesting that the use of fingerspelling has diminished over time. Across the Tasman Sea, only 2.5% of the corpus of New Zealand Sign Language was found to be fingerspelling. Fingerspelling has only become a part of NZSL since the 1980s; prior to that, words could be spelled or initialised by tracing letters in the air. Fingerspelling does not seem to be used much in the sign languages of Eastern Europe, except in schools, and Italian Sign Language is also said to use very little fingerspelling, and mainly for foreign words. Sign languages that make no use of fingerspelling at all include Kata Kolok and Ban Khor Sign Language.
The speed and clarity of fingerspelling also varies between different signing communities. In Italian Sign Language, fingerspelled words are relatively slow and clearly produced, whereas fingerspelling in standard British Sign Language (BSL) is often rapid so that the individual letters become difficult to distinguish, and the word is grasped from the overall hand movement. Most of the letters of the BSL alphabet are produced with two hands, but when one hand is occupied, the dominant hand may fingerspell onto an "imaginary" subordinate hand, and the word can be recognised by the movement. As with written words, the first and last letters and the length of the word are the most significant factors for recognition.
When persons fluent in sign language read fingerspelling, they do not usually look at the signer's hand(s), but maintain eye contact and look at the face of the signer as is normal for sign language. People who are learning fingerspelling often find it impossible to understand it using just their peripheral vision and must look directly at the hand of someone who is fingerspelling. Often, they must also ask the signer to fingerspell slowly. It frequently takes years of expressive and receptive practice to become skilled with fingerspelling.

# History
Some writers have suggested that the body and hands were used to represent alphabets in Greek, Roman, Egyptian and Assyrian antiquity. Certainly, "finger calculus" systems were widespread, and capable of representing numbers up to 10,000; they are still in use today in parts of the Middle East. The practice of substituting letters for numbers and vice versa, known as gematria, was also common, and it is possible that the two practices were combined to produce a finger calculus alphabet. The earliest known manual alphabet, described by the Benedictine monk Bede in 8th century Northumbria, did just that. While the usual purpose of the Latin and Greek finger alphabets described by Bede is unknown, they were unlikely to have been used by deaf people for communication  even though Bede lost his own hearing later in life. Historian Lois Bragg concludes that these alphabets were "only a bookish game."
Beginning with R. A. S. Macalister in 1938, several writers have speculated that the 5th century Irish Ogham script, with its quinary alphabet system, was derived from a finger alphabet that predates even Bede.
European monks from at least the time of Bede have made use of forms of manual communication, including alphabetic gestures, for a number of reasons: communication among the monastery while observing vows of silence, administering to the ill, and as mnemonic devices. They also may have been used as ciphers for discreet or secret communication.  Clear antecedents of many of the manual alphabets in use today can be seen from the 16th century in books published by friars in Spain and Italy. From the same time, monks such as the Benedictine Fray Pedro Ponce de Leon began tutoring deaf children of wealthy patrons  in some places, literacy was a requirement for legal recognition as an heir  and the manual alphabets found a new purpose. They were originally part of the earliest known Mouth Hand Systems. The first book on deaf education, published in 1620 in Madrid, included a detailed account of the use of a manual alphabet to teach deaf students to read and speak.
Meanwhile in Britain, manual alphabets were also in use for a number of purposes, such as secret communication, public speaking, or used for communication by deaf people. In 1648, John Bulwer described "Master Babington", a deaf man proficient in the use of a manual alphabet, "contryved on the joynts of his fingers", whose wife could converse with him easily, even in the dark through the use of tactile signing. In 1680, George Dalgarno published Didascalocophus, or, The deaf and dumb mans tutor, in which he presented his own method of deaf education, including an "arthrological" alphabet, where letters are indicated by pointing to different joints of the fingers and palm of the left hand. Arthrological systems had been in use by hearing people for some time; some have speculated that they can be traced to early Ogham manual alphabets. The vowels of this alphabet have survived in the contemporary alphabets used in British Sign Language, Auslan and New Zealand Sign Language. The earliest known printed pictures of consonants of the modern two-handed alphabet appeared in 1698 with Digiti Lingua, a pamphlet by an anonymous author who was himself unable to speak. He suggested that the manual alphabet could also be used by mutes, for silence and secrecy, or purely for entertainment. Nine of its letters can be traced to earlier alphabets, and 17 letters of the modern two-handed alphabet can be found among the two sets of 26 handshapes depicted.
Charles de La Fin published a book in 1692 describing an alphabetic system where pointing to a body part represented the first letter of the part (eg. Brow=B), and vowels were located on the fingertips as with the other British systems. He described codes for both English and Latin.
By 1720, the British manual alphabet had found more or less its present form. Descendants of this alphabet have been used by deaf communities (or at least in classrooms) in former British colonies India, Australia, New Zealand, Uganda and South Africa, as well as the republics and provinces of the former Yugoslavia, Grand Cayman Island in the Caribbean, Indonesia, Norway, Germany and the USA.

# Latin alphabet
There are two families of manual alphabets used for representing the Latin alphabet in the modern world. The more common of the two is mostly produced on one hand, and can be traced back to alphabetic signs used in Europe from at least the early 15th century. The alphabet, first described completely by Spanish monks, was adopted by the Abbe de l'Epee's deaf school in Paris in the 18th century, and was then spread to deaf communities around the world in the 19th and 20th centuries via educators who had learnt it there. Over time, variations have emerged, brought about by natural phonetic changes that occur over time, adaptions for local written forms with special characters or diacritics, and avoidance of handshapes that are considered obscene in some cultures. Modern descendants include the American manual alphabet and the International manual alphabet.
Several different two-handed manual alphabets are used by a number of deaf communities around the world. In many of these places, such as countries of the former Yugoslavia and in Turkish Sign Language, the vowels are represented by iconic signs, whereas in the BANZSL group of languages they are represented by pointing to the fingertips.

# Other alphabets
Manual alphabets based on the Arabic alphabet, the Ethiopian syllabary and the Korean Hangul syllabary-alphabet use handshapes that are more or less iconic representations of the characters in the writing system. Some manual representations of non-Roman scripts such as Chinese, Japanese, Indian Nagari, Hebrew, Greek, Thai and Russian alphabets are based to some extent on the one-handed Roman alphabet described above.