How does sign language work?

People who are hearing impaired communicate with the help of gestures – energetic movements of the hand accompanied by a lively facial expression. Like every other language, gestures must also be learnt. While speaking a person may need a lot of words to say ‘shall we cross the bridge’, but a single gesture suffices for the deaf. This language is also used at places where listening is not possible: under water by divers or in space by astronauts.