Many hearing people have the false impression that Sign Language is a worldwide universal language, but this however is far from the truth. Because of the isolated nature of Sign Language there is even significant variation from city to city within Britain, this is known as regional variation (for example, Scottish Signs, Manchester Signs, Welsh Signs, London Signs) and can be thought of as being similar to regional accents and colloquialisms found in spoken languages. Other countries have their own sign language.
When Deaf people communicate with other Deaf people from other nations they often use International Sign (IS). IS is a contact form of signing/communication system (as distinct from a full language) used at international meetings such as the World Federation of the Deaf (WFD) Congress and events such as the Deaflympics.