diglossia

thumb|upright=1.3|The station board of Hapur Junction railway station in [[North India demonstrating digraphia of two formal registers, Hindi and Urdu, of a common vernacular, Hindustani, an example of triglossia.]]

In linguistics, diglossia ( , ) is where two dialects or languages are used (in fairly strict compartmentalization) 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 lect (labeled "H" or "high") is used in certain situations such as literature, formal education, or other specific settings, but not used normally for ordinary conversation. The H variety may have no native speakers within the community. In cases of three dialects, the term triglossia is used. When referring to two writing systems coexisting for a single language, the term digraphia is used.