nonincidental

Nonincidental is an adjective meaning not incidental; not arising as a byproduct or happening by chance. It describes something that is central, intentional, or essential to a purpose, plan, or context, as opposed to something peripheral or accidental.

In formal writing, nonincidental is used to contrast with incidental. In medicine and research, writers may describe findings, effects, or goals as nonincidental when they are expected or deliberately sought as part of the objective, rather than unexpected, ancillary results. For example, a nonincidental outcome would be a result directly linked to the intervention under study, whereas incidental findings are unrelated outcomes discovered in the course of examination but not targeted by the study. In law and policy, the term can appear in discussions about obligations that are nonincidental to a duty, meaning they are a core component of the duty.

Origin and form: The word is formed from the prefix non- plus the adjective incidental, which comes from Latin incidental-, from incidere “to happen or fall upon.” The term is relatively rare in everyday speech and is more common in technical or formal contexts. See also incidental, intentional, deliberate, essential, core.