modality (n.)

A term used in GRAMMATICAL and SEMANTIC analysis to refer to contrasts in MOOD signalled by the VERB and associated categories. In English, modal contrasts are primarily expressed by a subclass of AUXILIARY verbs, e.g. may, will, can. This subclass is symbolized as M in the PHRASE-STRUCTURE RULES of a GENERATIVE grammar. Modal verbs share a set of morphological and syntactic properties which distinguish them from the other auxiliaries, e.g. no -s, -ing or -en forms. In CASE grammar, modality refers to one of the two major CONSTITUENTS of a sentences’s DEEP STRUCTURE, the other being PROPOSITION.