the coexistence of two forms of the same language in a speech community. Often, one form is the literary or prestige dialect, and the other is a common dialect spoken by most of the population. Such a situation exists in many speech communities throughout the worlde.g., in Greece, where Katharevusa, heavily influenced by Classical Greek, is the prestige dialect and Demotic is the popular spoken language, and in Egypt, where there are two dialects of Arabic. Sociolinguists may also use the term diglossia to denote bilingualism, the speaking of two or more languages by the members of the same community, as, for example, in New York City, where many members of the Hispanic community speak both Spanish and English, switching from one to the other according to the social situation or the needs of the moment.
DIGLOSSIA
Meaning of DIGLOSSIA in English
Britannica English vocabulary. Английский словарь Британика. 2012