nongrammatical

Nongrammatical is an adjective describing utterances or constructions that do not conform to the grammatical rules of a language, or to a specific grammar being applied. It is closely related to ungrammatical, but is often used to emphasize deviation from a prescriptive standard or from a defined grammatical framework rather than from a speaker’s idiolect alone.

Orthography and usage vary. Some writers hyphenate as non-grammatical; others join as nongrammatical. The choice can reflect stylistic conventions, dialect considerations, or the field of study (linguistics, language pedagogy, computational linguistics).

In linguistics, nongrammatical constructions are analyzed to identify which rule or parameter they violate. In language teaching, highlighting nongrammatical forms helps learners correct errors. In natural language processing, systems may assign a low grammaticality score or flag nongrammatical outputs for revision. For example, “She going to school” is nongrammatical in Standard English, which normally requires the auxiliary “is” for the present progressive: “She is going to school.”

Nongrammaticality is distinct from semantic anomaly; a sentence can be grammatical but semantically odd, or vice versa. The term primarily anchors discussions of grammar within a given linguistic theory or community and is used to distinguish departures from the expected grammatical structure from other kinds of language deviations.