Diglossia

In linguistics, diglossia ( /daɪˈɡlɒsiə/; Greek: διγλωσσία < δύο+γλώσσα, two languages) refers to a situation in which two dialects or usually closely related languages are used by a single language community. In addition to the community's everyday or vernacular language variety (labeled "L" or "low" variety), a second, highly codified variety (labeled "H" or "high") is used in certain situations such as literature, formal education, or other specific settings, but not used for ordinary conversation.

The high variety may be an older stage of the same language (e.g. Latin in the early Middle Ages), or a distinct yet closely related present day dialect (e.g. Norwegian with Bokmål and Nynorsk, or Chinese with Mandarin as the official, literary standard and colloquial topolects/dialects used in everyday communication). Other examples include literary Katharevousa versus spoken Demotic Greek, the Dravidian Languages Kannada, Tamil and Telugu of southern India, with their high and low registers, and the triglossia of Arabic with the Classical Arabic of religion, the journalistic and literary Modern Standard Arabic, and the various regional spoken Arabic languages.