What term describes a version of a language used by a specific group of people?

A dialect is indeed the term used to describe a version of a language that is particular to a specific group of people. It encompasses not only distinct vocabulary and pronunciation but also unique grammatical structures and expressions that might set it apart from standard forms of the language. Dialects can reflect regional, cultural, social, or ethnic identities, illustrating how language evolves in different environments and communities.

Other terms listed have different connotations. Grammar refers to the set of rules that govern the structure of a language, not a variation within it. Slang denotes informal language that may arise within particular groups, often as a means of identity or to convey familiarity. Accent specifically pertains to the way words are pronounced, rather than the broader linguistic features associated with dialects. Thus, dialect most accurately captures the essence of a language variation tied to a specific group.