The idea that a single, universal sign language exists is a common misunderstanding. Just as there are thousands of distinct spoken languages, there are hundreds of unique sign languages, each with its own grammar, vocabulary, and cultural identity. These visual languages are not simply signed versions of the spoken language in a given region. They are fully developed, natural languages that have evolved independently within Deaf communities.
The Answer: A World of Diverse Sign Languages
Linguists estimate that there are over 300 distinct sign languages used worldwide, and this number is not known with certainty because new ones continue to emerge. These languages are not mutually intelligible. For example, American Sign Language (ASL) and British Sign Language (BSL) are entirely different languages, despite the United States and the United Kingdom sharing the English spoken language.
ASL is used predominantly in the United States and parts of Canada, while BSL is the language of the Deaf community in the United Kingdom. These two languages do not even belong to the same language family, making them as different from each other as English is from Japanese. Other major sign languages include French Sign Language (LSF), Chinese Sign Language (CSL), and Australian Sign Language (Auslan).
Sign languages possess all the linguistic properties of spoken languages, including complex syntax, morphology, and phonology. They are not artificial systems but have emerged organically from the need for visual communication within Deaf communities.
The Roots of Linguistic Diversity
The primary reason for the vast diversity in sign languages is their independent historical development, often driven by the establishment of schools for the deaf in different countries. In the early 19th century, American Sign Language (ASL) was formed from a blend of local sign systems and Old French Sign Language (LSF), brought over by French educator Laurent Clerc. This historical connection means that ASL shares more similarities with LSF than it does with BSL, which developed separately in the United Kingdom.
Geographical isolation also played a significant role in the divergence of these languages before widespread travel and communication became common. In regions like Martha’s Vineyard in the United States, high rates of hereditary deafness led to the development of unique village sign languages used by both deaf and hearing residents. These localized systems contributed to the regional variations that eventually merged into national sign languages.
Sign languages are primarily transmitted face-to-face within a community, which naturally leads to localized variations and evolution over time. Unlike spoken languages, which have a long history of being standardized through written forms, sign languages have historically lacked this stabilizing influence. This reliance on community transmission allows for rapid linguistic change and the emergence of distinct dialects and languages.
How Sign Languages Differ
The differences between sign languages are evident across all levels of linguistic structure, starting with the lexicon, or vocabulary. The sign for a common concept like “water” or “mother” in ASL is often completely different from the sign used in BSL or LSF. Even the manual alphabets used for fingerspelling differ significantly; ASL uses a one-handed system, while BSL and Auslan use a two-handed system to represent the letters of the alphabet.
Grammar and syntax also vary substantially between sign languages, reflecting different ways of structuring a sentence. For example, American Sign Language often uses a Topic-Comment structure, where the subject is established first, followed by the action or information about it. This structure is distinct from the word order found in other sign languages, and it is not a direct translation of the spoken language in the same region.
A third area of difference lies in the use of non-manual markers (NMMs), which include facial expressions, body postures, and mouth movements that function grammatically. These markers are not merely emotional expressions but are used to convey questions, negation, or adverbs. The specific facial movements required to indicate a question in one sign language may be entirely different from those used for the same purpose in another.