modality

Modality is the quality of a statement that expresses possibility, necessity, or other related attitudes toward the truth of a proposition or the conduct of an action. The domain spans philosophical questions, formal logic, and linguistic expression, as well as disciplines that study knowledge, obligation, or capability.

In philosophy, modality investigates what could be the case (possibility) or must be the case (necessity), often using possible-world semantics. It distinguishes alethic modalities (possibility, necessity, contingency), deontic modality (obligation, permission), and epistemic modality (what is known or inferred). Modal logic formalizes these notions with operators such as □ (necessarily) and ◇ (possibly).

In linguistics, modality is encoded by mood or auxiliary verbs and other markers. Epistemic modality conveys certainty or speculation (might, may, probably); deontic modality expresses obligation or permission (must, may); dynamic modality covers ability and volition (can, will). Modality interacts with tense, aspect, and cross-linguistic grammar; some languages rely on particles, evidentials, or verb inflection rather than separate modal verbs.

Usage is sensitive to context and scope; a single utterance can have different modal readings depending on factors such as aspect and speaker stance. Distinctions between may and might or must and have to illustrate subtle differences in certainty, necessity, and source of claim.

Modality provides a framework for analyzing how truth values are qualified beyond simple assertion, across language and logic.