diglossia

Diglossia is a sociolinguistic arrangement in which a community uses two distinct varieties of the same language for different social functions. The term, introduced by Charles A. Ferguson in 1959, identifies a high variety (H) and a low variety (L). The H variety is typically used in formal settings such as education, literature, religious services, and official discourse, while the L variety is used in everyday conversation, family interaction, and informal settings. Although they are related, the two varieties often differ in lexicon, pronunciation, grammar, and stylistic norms, and they tend to be maintained as separate codes within the community. Children usually acquire both varieties naturally, with literacy and schooling often conducted in H.

In stable diglossic systems, the H variety is more codified and taught, whereas the L variety is learned in the home and community. Language switching tends to follow social context, and domains of use are functionally distinct. The concept highlights how prestige, education, and media reinforce the separation between varieties.

Commonly cited examples include Arabic-speaking communities, where Modern Standard Arabic functions as H and local dialects as L; in the German-speaking world, Standard German serves as H and regional dialects as L; in Haiti, French is used in formal domains and Haitian Creole in daily life, though Creole is often treated as a separate language by speakers and scholars. Some researchers describe extended or multi-variate forms of diglossia when more than two varieties are involved, and debates continue about the rigidity of the framework in contemporary multilingual societies.