Sign language

Sign languages (also known as signed languages) are languages that use the visual-manual modality to convey meaning. Sign languages are expressed through manual articulations in combination with non-manual elements. Sign languages are full-fledged natural languages with their own grammar and lexicon. Sign languages are not universal and they are not mutually intelligible with each other, although there are also striking similarities among sign languages.–1? Sign languages (also known as signed languages) are languages that use the visual-manual modality to convey meaning. Sign languages are expressed through manual articulations in combination with non-manual elements. Sign languages are full-fledged natural languages with their own grammar and lexicon. Sign languages are not universal and they are not mutually intelligible with each other, although there are also striking similarities among sign languages. Linguists consider both spoken and signed communication to be types of natural language, meaning that both emerged through an abstract, protracted aging process and evolved over time without meticulous planning. Sign language should not be confused with body language, a type of nonverbal communication. Wherever communities of deaf people exist, sign languages have developed as handy means of communication and they form the core of local deaf cultures. Although signing is used primarily by the deaf and hard of hearing, it is also used by hearing individuals, such as those unable to physically speak, those who have trouble with spoken language due to a disability or condition (augmentative and alternative communication), or those with deaf family members, such as children of deaf adults. It is unclear how many sign languages currently exist worldwide. Each country generally has its own native sign language, and some have more than one. The 2013 edition of Ethnologue lists 137 sign languages. Some sign languages have obtained some form of legal recognition, while others have no status at all. Linguists distinguish natural sign languages from other systems that are precursors to them or derived from them, such as invented manual codes for spoken languages, home sign, 'baby sign', and signs learned by non-human primates. 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?' Until the 19th century, most of what is known about historical sign languages is limited to the manual alphabets (fingerspelling systems) that were invented to facilitate transfer of words from a spoken language to a sign language, rather than documentation of the language itself. Pedro Ponce de León (1520–1584) is said to have developed the first manual alphabet. In 1620, Juan Pablo Bonet published Reducción de las letras y arte para enseñar a hablar a los mudos (‘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 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.