What is the difference between body language and sign language?

Human beings and animals communicate a lot through their body postures. An angry cat humps its back and ruffles its skin up to look bigger and more dangerous warning its opponent not to attack. Humans frown in doubt and smile when they feel happy. We use thumb up or thumb down as common gestures of approval or disapproval. We also make use of universal sign language, we know what an index finger on the lips or a waving hand is trying to tell us .But signs do not mean the same globally. If you make an “o” with the index finger and the thumb it means OK in USA but in other places it is an insult.

People who are hearing impaired communicate with the help of gestures or sign language. The sign language involves movements of hands accompanied by lively facial expression. In a sign language gestures are learnt. Speaking involves a lot of vocabulary to say, “shall we cross the bridge” but a single gesture suffices for the deaf. Sign language is also used in places where listening becomes impossible for instance divers under water and astronauts in space use such kind of language.