Look a little closer
Sign languages are not one shared picture code that translates speech into gestures. They are full natural languages developed across generations in Deaf communities, so vocabulary and grammar differ with region and history.
Meaning involves more than hand shape. Location, orientation, movement and interaction between the hands distinguish signs, while facial expression and head or body movement can carry questions and grammatical relationships.
Separated communities change independently just as spoken-language communities do. Schools, migrating teachers and contact among signers can blend or split languages, creating distinct histories.
Countries sharing a spoken language do not necessarily share a sign language. American Sign Language has historical links to French Sign Language but differs greatly from British Sign Language; American and British signers do not automatically understand each other.
Conversely, regions with different spoken languages may use historically related sign languages. Sign-language families often follow networks of Deaf schools and communities rather than borders drawn by surrounding speech.
International Sign can assist communication at global events, but it is not one native language serving every setting. That is why interpreting services must specify exactly which sign languages are involved.
