alethic  (adj.)

A term derived from modal logic and used by some LINGUISTS as part of a theoretical framework for the analysis of MODAL VERBS and related STRUCTURES in LANGUAGE. Alethic modality is concerned with the necessary or contingent truth of propositions, e.g. the use of the modal in the sentence A triangle must have three sides, i.e. ‘It is impossible for a triangle not to have three sides.’ It contrasts with EPISTEMIC and DEONTIC modality, which are concerned with obligation and knowledge, respectively.