Informal language is language use characterized by:
(English)
Here are some examples of language domains where informal language takes place:
Ferguson, Charles A. 1959. "Diglossia." Word.
Fasold, Ralph. 1984.The sociolinguistics of society. Oxford: Basil Blackwell.
Crystal, David. 1985.A dictionary of linguistics and phonetics. 2nd edition. New York: Basil Blackwell.
Britto, Francis. 1986.Diglossia: A study of the theory with application to Tamil. Washington, DC: Georgetown University.