This document discusses the concept of diglossia in sociolinguistics. Diglossia refers to a stable language situation where two varieties of the same language or two separate languages occupy different functional roles. A "high" superposed variety is used for formal contexts like sermons, lectures, and literature, while a "low" variety is used for everyday conversations. Three conditions typically lead to diglossia: a large written literature, restricted literacy, and establishment over centuries. Speakers often regard the high variety as superior and deny the existence of the low variety. Fishman extended the concept to bilingual communities where languages have hierarchical prestige.