Discourse

Blommaert, J., 2005, Discourse: A Critical Introduction, Cambridge, Cambridge University Press

Language varieties
a) Varieties identified on the basis of the modes or channels of communication: spoken versus written, direct versus indirect (mediated) communication, etc.
b) Geographically identified varieties – ‘dialects’, regional accents
c) Socially identified varieties often called ‘sociolects’ – class varieties, professional jargons, peer-group talk, age-, gender-, or ethnically marked varieties, etc.
d) Situationally or domain-identified varieties, i.e. varieties used on particular occasion or in particular social domains, such as peer-group talk, dinner table conversations, doctor-patient interactions, classroom interactions etc.
e) Styles, genres, formats of communication – formal versus informal varieties, storytelling, jokes, casual chat, public speech, media discourse, etc.
Every chunk of real language will carry all these features at the same time.