Classes of English ...

Acrolect

the variety of speech that is closest to a standard prestige language, especially in an area in which a creole is spoken. For example, Standard Jamaican English is the acrolect where Jamaican Creole is spoken.

Mesolect 

It is term referring to a register or range of registers of spoken language whose character falls somewhere between the prestige of the acrolect and the informality of the basilect. Mesolectic speech, where it is distinguished from acrolectic speech, is often the most widely spoken form of a language, generally being used by lower and lower-middle classes. Within the context of creole lanuages, mesolects only appear in instances of a post-creole speech continuum wherein speakers code-switch between various mesolectal levels within the continuum depending on context.

Basilect

is a dialect of speech that has diverged considerably from an acrolect, or standard, "educated", variety of the language. A basilect and the acrolect in which it originated may eventually reach mutual unintelligibility.