According to Joshua Fishman(1967), diglossia is a situation in which a community uses two different languages, not just one language with its dialect, for different social purposes. One language is considered the high (H) variety and is used in formal contexts such as education, politics, and religion, while the low (L) variety is used in everyday informal communication and social interaction at home. Fishman explains that speakers in such communities are usually bilingual, meaning they master both languages and switch between them depending on the situation and context. He also notes that diglossia and bilingualism can exist together or separately within a society.
According to Joshua Fishman, diglossia in Algerian society can be seen in the use of Arabic and French languages . Arabic used as Modern Standard Arabic and the local dialects, functions mainly as the low (L) variety and is used in daily communication and cultural life, while French represents the high variety (H) and is often used in formal domains such as higher education,Universities, administration, and professional settings. Many Algerians are bilingual and switch between the two languages depending on the situation. This functional separation of languages clearly illustrates Fishman’s idea that diglossia occurs when different languages serve different social purposes within the same community.