Diglossia is a sociolinguistic situation in which two varieties of the same language (or two closely related languages) coexist in a community, each serving distinct social functions. The term was formalised by Charles Ferguson (1959) in his foundational paper "Diglossia" in Word.
Ferguson identified two varieties:
| Feature | High (H) variety | Low (L) variety |
|---|---|---|
| Function | Formal settings: education, government, religion, literature, news | Informal settings: daily conversation, family, marketplace |
| Acquisition | Learned through formal education | Acquired naturally as mother tongue |
| Standardisation | Codified grammar, dictionaries, literary canon | Largely uncodified; may lack a standard written form |
| Prestige | High: associated with education, culture, authority | Low: associated with informality, intimacy, solidarity |
| Stability | Highly stable: diglossic situations can persist for centuries | Stable in speech; may be under pressure from H in media |
| Community | H variety | L variety |
|---|---|---|
| Arabic-speaking countries | Modern Standard Arabic (fusha) | Regional dialects (aamiya/darija) |
| Switzerland (German) | Standard German (Hochdeutsch) | Swiss German (Schwyzerdütsch) |
| Haiti | French | Haitian Creole |
| Greece (historical) | Katharevousa | Demotic Greek |
Ferguson characterised diglossia through nine defining features:
Joshua Fishman broadened the concept beyond varieties of the same language to include situations where two unrelated languages serve H and L functions: for example, Spanish (H) and Guarani (L) in Paraguay, or English (H) and local languages (L) in many postcolonial contexts.
This extended sense is directly relevant to ELT: in many World Englishes contexts, English functions as an H variety alongside local L varieties.