occasional

Occasional is an English adjective meaning happening or done now and then; occurring at irregular or infrequent intervals. It describes events, actions, or items that are not regular or constant but occur from time to time. Examples include an occasional headache, occasional rain, or an occasional visitor.

The adverb form is occasionally, used to modify verbs: It rains occasionally in spring. Occasionally is more common in everyday speech; occasional is not used as an adverb in standard grammar.

Etymology traces occasional to Middle English, via Old French occasionnel, from Latin occasionālis “of opportunity,” based on occasio “opportunity.” The sense developed to mean something that happens as a matter of opportunity or chance, later conditioning its use to infrequent or irregular occurrences.

Usage notes and synonyms: occasional implies irregularity rather than rarity, and it is often used to describe people, events, or items that appear sporadically. Related terms include sporadic (scattered in time or space), intermittent (starting and stopping), and infrequent (not occurring often). Occasional contrasts with frequent or regular occurrences and with continuous or constant action.

See also: occasionality (the quality of being occasional), occasionally (adverb), synonyms and nuanced usage in style guides.