There are currently about 400 languages in the world with fewer than 100 speakers. In societies where two or more languages are used, the number of speakers of one of these languages may decline to the point where it is no longer used and may even disappear. In sign languages, the appearance and disappearance of languages is more frequent than in spoken languages. It is said that when the number of hearing impaired people exceeds 3% of the population, visual communication methods begin to develop, and when there are no more hearing impaired people, the language disappears.