irregular (adj.)

A term used in LINGUISTICS to refer to a linguistic FORM which is an exception to the pattern stated in a RULE. For example, VERBS such as took, went, saw, etc., are irregular, because they do not follow the rule which forms the past TENSE by adding -ed. GRAMMAR is concerned with the discovery of REGULAR PATTERNS in linguistic DATA: lists of irregularities are usually avoided, and handled by incorporating the exceptional information into a dictionary entry.