Sign languages, plural, because every country has its own sign language, and some countries have more than one, for example Belgium with Flemish (VGT) and French Belgian Sign Language (LSFB) , and Spain with Spanish (LSE) and Catalan Sign Language (LSC).
Sign languages are natural languages each with its own lexicon and grammar. Sign languages have in common that they use the hands, face and body as 'articulators'.
Sign language is NOT :
- universal. There are between 138 and 300 different sign languages being used around the world.
- a word-by-word translation of a spoken language. In education, teachers sometimes speak and sign at the same time to teach children the spoken language in a visual way. To transmit the exact surface structure of a spoken sentence (instead of its meaning) - for example to sign articles, function words and affixes and suffixes - artificial and usually cumbersome signs have been invented. This is not sign language, but an artificial, and for sign language users unnatural code, usually called 'signed English', 'signed French', etc.
- a letter-by-letter spelling of words. Letter-by-letter spelling is called fingerspelling and is used for instance for names.