Which term best captures the concept of ordinary, non-literary language?

The term that best captures the concept of ordinary, non-literary language is "vernacular." Vernacular refers to the language or dialect spoken by the ordinary people in a particular region or community. It encompasses the everyday speech used in casual contexts, contrasting with more formal or artistic speech that might be found in literature or poetry. This term emphasizes the natural, familiar way in which people communicate, making it accessible and relatable.

The other terms do not align with the concept of ordinary language. "Verbose" refers to the use of more words than necessary, often leading to overly complicated or lengthy expressions. "Urbane" describes someone who is sophisticated, refined, or polished in manners, which does not relate to the concept of ordinary speech. "Untenable" means something that is not able to be maintained or defended, which has no connection to language types. Overall, vernacular is the most accurate representation of everyday, approachable language.