Accent - A speech variety differing in its pronunciation from other varieties. The variation may be due to regional factors, (a London, Geordie, Somerset, etc. accent), social factors (an RP accent), whether a speaker is a native speaker or not (a French, Chinese, etc. accent). Varieties differing grammatically are usually referred to as dialects. Accent and dialect typically go together, but need not do so.
Dialect - A form of a language differentiated from the See also standard language by particular features of grammar, vocabulary and accent and associated with a particular region.
Grammar - In its narrow sense, the structure of sentences (syntax) and the structure of words (morphology) in a language. The sense introduced by Chomsky, the set of rules known by (internalized by) the members of a speech community
Idioms - Fixed expressions whose meaning cannot be guessed from their individual words. Fixed expression is a general term, along with ‘set expression’, for combinations of words that cannot be changed in any way, or that can only be changed in minor detail. For example, "speak of the devil," "we'll cross that bridge when we come to it," "a dime a dozen," "Go back to the drawing board," etc.
Linguistic Imperialism - The relationship between dominated and dominating cultures, and hence languages. The concept is often used to explain the widespread use of English but it is equally applicable to such languages as Latin, classical Greek, French, Spanish and Mandarin Chinese.
Mother Tongue - The first language acquired by a speaker in childhood.
Native Language - The first language acquired by a child, typically from its mother.
Official Language - A language that has legal status in a nation’s courts, parliament, administration and so on, such as Gaelic in Ireland.
Slang - Words and phrases used by speakers of standard and non-standard varieties, most often in very informal speech. Slang expressions are created and disappear relatively quickly, though some persist.
Standard Language - The dialect normally used by educated native speakers. It is usually recognized by its lexical and grammatical properties, codified in grammars and dictionaries, rather than by accent. Thus standard English tends to be relatively homogeneous throughout the English-speaking world, but may be spoken with, say, a Scots, Yorkshire or Australian accent.
Brown, E. K., and J. E. Miller. The Cambridge Dictionary of Linguistics, Cambridge University Press, 2013. EBSCOhost