What term refers to any distinct variety of a language spoken in a specific region?

The term that refers to any distinct variety of a language spoken in a specific region is "dialect." A dialect encompasses the specific vocabulary, grammar, and pronunciation variations that are characteristic of a particular geographic area or social group. Dialects often arise due to historical, cultural, and social factors, leading to differences that may be significant enough to distinguish one group of speakers from another.

Slang, while related to language, represents informal expressions or colloquialisms that may not be universally understood or accepted within the larger language community. It does not necessarily pertain to the broader and more systematic variations within a language based on region.

An accent specifically refers to the way words are pronounced in a language, which can reflect the speaker's regional background but does not encompass the broader linguistic characteristics of grammar and vocabulary inherent in a dialect.

An idiom is a phrase or expression that has a figurative meaning different from its literal meaning. While idioms are part of the vocabulary used in various dialects, they do not represent a variety of language based on regional differences.