diglossia
The coexistence in a given population of two closely related native languages or dialects, one of which is regarded as more prestigious than the other; the similar coexistence of two unrelated languages.
uncountable
It is the purpose of this chapter to relate these two research traditions to each other by tracing the interaction between their two major constructs: bilingualism (on the part of psychologists) and diglossia (on the part of sociologists).
2000, Joshua A. Fishman, Chapter 3: Bilingualism with and without diglossia; diglossia with and without bilingualism, Li Wei (editor), The Bilingualism Reader, Taylor & Francis (Routledge), page 81,The presence of a cleft or doubled tongue.
uncountable
Where it comes from
From Latin diglōssia. In linguistics introduced 1959 by Charles A. Ferguson, based on French diglossie, from Ancient Greek δίγλωσσος (díglōssos, “bilingual”) + -ία (-ía). Equivalent to di- + -glossia.
Adapted from the Wiktionary entry diglossia (CC BY-SA 4.0).