“Vernacular (noun): Native or regional idiom, on nonstandard or substandard language, as opposed to the established, cultured language of a society; spoken, as opposed to literary, usage; everyday speech; a lingo. Adjective: vernacular; adverb: vernacularly; noun: vernacularity.”
Excerpted from: Grambs, David. The Random House Dictionary for Writers and Readers. New York: Random House, 1990.