Coexistence of two varieties of the same language in a speech community, with each variety being more or less standardized and occupying a distinct sociolinguistic niche.
Typically, one variety is more formal or prestigious while the other is more suited to informal conversation or is taken as a mark of lower social status or less education. Classic diglossic situations can be found in Arabic -speaking communities, where Modern Standard Arabic coexists with dozens of regional Arabic dialects, and among speakers of Dravidian languages such as Tamil , where different words for basic concepts such as "house" or "water" are chosen depending on the speaker's caste or religion.