A vernacular or vernacular language is in contrast with a "standard language." It refers to the language or dialect that is spoken by people who are inhabiting a particular country or region. The vernacular is typically the native language, normally spoken informally rather than written, and seen as of lower status than more codified forms. It may vary from more prestigious speech varieties in different ways, in that the vernacular can be a distinct stylistic register, a regional dialect, a sociolect, or an independent language. Vernacular is a term for a type of speech variety, generally used to refer to a local language or dialect, as distinct from what is seen as a standard language. The vernacular is contrasted with higher-prestige forms of language, such as national, literary, liturgical or scientific idiom, or a lingua franca, used to facilitate communication across a large area.

According to another definition, a vernacular is a language that has not developed a standard variety, undergone codification, or established a literary tradition. In the context of language standardization, the terms "vernacular" and "vernacular dialect" are also used as alternative designations for "non-standard dialect".