A particular variety of a language that is regarded as the most correct way of writing or speaking the language. Open English WordNet

A standard language is a language variety that has undergone substantial codification of grammar and usage, although occasionally the term refers to the entirety of a language that includes a standardized form as one of its varieties. Wikipedia

A particular variety of a language accepted as the institutionalized norm in a community Wikipedia Disambiguation

A language variety whose grammar and usage are codified Wikipedia Disambiguation

Language variety used by a population in their public discourse ; standardized language that has at least one standard variety besides its other varieties; variety that has undergone standardization Wikidata

A particular variety of a language that has been standardized by an academy or other institution. This is the version of a language that is taught in schools, to native and foreign language learners. Most texts written in that language follow its spelling and grammar norms. OmegaWiki

A form of a language that is institutionally promoted, regarded as the most "correct" or neutral variety; used by a population for public and formal purposes. Wiktionary