Sign languages (also known as signed languages) are languages that use the visual-manual modality to convey meaning rather than spoken words. They are expressed through manual articulation in combination with non-manual markers, and are full-fledged natural languages with their own grammar and lexicon. Sign languages are not universal and are usually not mutually intelligible, although there are similarities among different sign languages.
Wherever communities of deaf and hard of hearing people exist, sign languages have developed as a means of communication and form the core of local Deaf cultures. Although signing is used primarily by deaf and hard of hearing people, it is also used by hearing individuals, such as those with deaf family members including children of deaf adults (CODAs).
Sign languages are distinct from body language, a type of nonverbal communication. Linguists also distinguish natural sign languages from other systems that are precursors to them or derived from them, such as constructed manual codes for spoken languages, home sign, baby sign language, and signs used with non-human primates.
The number of sign languages worldwide is not precisely known. Each country generally has its own native sign language, and some have more than one. The 2021 edition of Ethnologue lists 150 sign languages, while the SIGN-HUB Atlas of Sign Language Structures lists over 200 and notes that there are more that have not yet been documented. As of 2021, Indo-Pakistani Sign Language is the most widely used sign language in the world, and Ethnologue ranks it as the 156th most spoken language in the world.
Some sign languages have obtained some form of legal recognition.
History
Groups of deaf people have used sign languages throughout history. One of the earliest written records of a sign language is from the fifth century BC, in Plato's Cratylus, where Socrates says: "If we hadn't a voice or a tongue, and wanted to express things to one another, wouldn't we try to make signs by moving our hands, head, and the rest of our body, just as dumb people do at present?" Most of what is known about pre-19th-century sign languages is limited to the manual alphabets (fingerspelling systems) that were invented to facilitate the transfer of words from a spoken language to a sign language, rather than documentation of the language itself.
Debate around European monastic sign languages developed in the Middle Ages has come to regard them as gestural systems rather than true sign languages. Monastic sign languages were the basis for the first known manual alphabet used in deaf schools, developed by Pedro Ponce de León.
The earliest records of contact between Europeans and Indigenous peoples of the Gulf Coast region in what is now Texas and northern Mexico note a fully formed sign language already in use by the time of the Europeans' arrival there. These records include the accounts of Cabeza de Vaca in 1527 and Coronado in 1541.
In 1620, Juan Pablo Bonet published ('Reduction of letters and art for teaching mute people to speak') in Madrid. It is considered the first modern treatise of sign language phonetics, setting out a method of oral education for deaf people and a manual alphabet.
In Britain, manual alphabets were also in use for a number of purposes, such as secret communication, public speaking, or communication by or with deaf people. In 1648, John Bulwer described "Master Babington", a deaf man proficient in the use of a manual alphabet, " on the 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 modern 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 (Latin for Language [or Tongue] of the Finger), 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 (e.g. Brow=B), and vowels were located on the fingertips as with the other British systems. He described such 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, at least in education, in the 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 United States.
During the Polygar Wars against the British, Veeran Sundaralingam communicated with Veerapandiya Kattabomman's mute younger brother, Oomaithurai, by using their own sign language.
Frenchman Charles-Michel de l'Épée published his manual alphabet in the 18th century, which has survived largely unchanged in France and North America until the present time. In 1755, Abbé de l'Épée founded the first school for deaf children in Paris; Laurent Clerc was arguably its most famous graduate. Clerc went to the United States with Thomas Hopkins Gallaudet to found the American School for the Deaf in Hartford, Connecticut, in 1817. Gallaudet's son, Edward Miner Gallaudet, founded a school for the deaf in 1857 in Washington, D.C., which in 1864 became the National Deaf-Mute College. Now called Gallaudet University, it is still the only liberal arts university for deaf people in the world.
International Sign, formerly known as Gestuno, is used mainly at international deaf events such as the Deaflympics and meetings of the World Federation of the Deaf. While recent studies claim that International Sign is a kind of a pidgin, they conclude that it is more complex than a typical pidgin and indeed is more like a full sign language.
Linguistics Sign languages have capability and complexity equal to spoken languages; their study as part of the field of linguistics has demonstrated that they exhibit the fundamental properties that exist in all languages.Klima, Edward S.; & Bellugi, Ursula. (1979). The signs of language. Cambridge, Mass.: Harvard University Press. . Such fundamental properties include duality of patterning and recursion.Bross, Fabian (2020). The clausal syntax of German Sign Language: A cartographic approach. Berlin: Language Science Press. pp. 37–38. Duality of patterning means that languages are composed of smaller, meaningless units which can be combined into larger units with meaning (see below). The term recursion means that languages exhibit grammatical rules and the output of such a rule can be the input of the same rule. It is, for example, possible in sign languages to create subordinate clauses and a subordinate clause may contain another subordinate clause.
Sign languages are not mime—in other words, signs are conventional, often arbitrary and do not necessarily have a visual relationship to their referent, much as most spoken language is not onomatopoeic. While iconicity is more systematic and widespread in sign languages than in spoken ones, the difference is not categorical. The visual modality allows the human preference for close connections between form and meaning, to be more fully expressive, whereas this is more suppressed in spoken language.
Sign languages, like spoken languages, organize elementary, meaningless units into meaningful semantic units. This type of organization in natural language is often called duality of patterning. As in spoken languages, these meaningless units are represented as (combinations of) features, although coarser descriptions are often also made in terms of five "parameters": handshape (or handform), orientation, location (or place of articulation), movement, and non-manual expression. These meaningless units in sign languages were initially called cheremes,Fabian Bross (2016). "Chereme" . In: Hall, T. A. Pompino-Marschall, B. (ed.): Dictionaries of Linguistics and Communication Science. Volume: Phonetics and Phonology. Berlin, New York: Mouton de Gruyter. from the Greek word for hand, by analogy to the phonemes, from Greek for voice, of spoken languages. Now they are sometimes called phonemes when describing sign languages too, since the function is essentially the same, but more commonly discussed in terms of "features" or "parameters". More generally, both sign and spoken languages share the characteristics that linguists have found in all natural human languages, such as transitoriness, semanticity, arbitrariness, productivity, and cultural transmission.
Common linguistic features of many sign languages are the occurrence of classifier constructions, a high degree of inflection by means of changes of movement, and a topic-comment syntax. More than spoken languages, sign languages can convey meaning by simultaneous means, e.g. by the use of space, two manual articulators, and the signer's face and body. Though there is still much discussion on the topic of iconicity in sign languages, classifiers are generally considered to be highly iconic, as these complex constructions "function as predicates that may express any or all of the following: motion, position, stative-descriptive, or handling information".Emmorey, K. (2002). Language, cognition and the brain: Insights from sign language research. Mahwah, N.J.: Lawrence Erlbaum Associates. The term classifier is not used by everyone working on these constructions. Across the field of sign language linguistics the same constructions are also referred with other terms such as depictive signs.
Today, linguists study sign languages as true languages, part of the field of linguistics. However, the category "sign languages" was not added to the Linguistic Bibliography/Bibliographie Linguistique until the 1988 volume, when it appeared with 39 entries.
Relationships with spoken languages
There is a common misconception that sign languages are spoken language expressed in signs, or that they were invented by hearing people. Similarities in language processing in the brain between signed and spoken languages further perpetuated this misconception. Hearing teachers in deaf schools, such as Charles-Michel de l'Épée or Thomas Hopkins Gallaudet, are often incorrectly referred to as "inventors" of sign language. Instead, sign languages, like all natural languages, are developed by the people who use them, in this case, deaf people, who may have little or no knowledge of any spoken language.