This is a terminological list that collects terms used to denote (types of) “communicative subsystems” of a language (a communicative system). Each of them may have its sphere of application, some of them might be synonymous, and also, when language is used in a broad sense, the objects denoted by the terms are languages.
A standard language (also standard dialect or standardized dialect) is a particular variety of a language that has been given either legal or quasi-legal status. ...
Dialect–language distinction
Dialect, language; idiom; Abstandsprache, Ausbausprache, Dachsprache. A dialect (from the Greek word διάλεκÏοÏ, dialektos) is a variety of a language used by people from a particular geographic area. ... Abstandsprache (also called abstand language) is a language form that is so different from every other language that it cannot be regarded as a dialect of any another language, whether or not it is itself an Ausbausprache (almost identical with standard language). ... An Ausbausprache (also called an ausbau language) is a language which has a standard spelling, a standard grammar and a relatively wide and clear vocabulary (and is thus almost identical with a standard language). ... Dachsprache means a language form that serves as standard language for different dialects, mostly in a dialect continuum, even though these dialects may be so different that mutual intellegibility is not possible on the basilectal level between all dialects. ...
A variety of a language is a form that differs from other forms of the language systematically and coherently.
Variety is a wider concept than style of prose or style of language.
Varieties such as dialects, idiolects, and sociolects can be distinguished not only by their vocabulary, but also by differences in grammar, phonology and prosody.