in·ci·den·tal / ˌinsiˈdentl/ • adj. 1. accompanying but not a major part of something: for the fieldworker who deals with real problems, paperwork is incidental incidental expenses. ∎ occurring by chance in connection with something else: the incidental catch of dolphins in the pursuit of tuna. 2. (incidental to) liable to happen as a consequence of (an activity): the ordinary risks incidental to a fireman's job. • n. (usu. incidentals) an incidental detail, expense, event, etc.: an allowance to cover meals, taxis, and other incidentals.
Contingent upon or pertaining to something that is more important; that which is necessary, appertaining to, or depending upon another known as the principal.
Under workers' compensation statutes, a risk is deemed incidental to employment when it is related to whatever a worker must do in order to fulfill the employment contract, but is not the primary function that the worker was hired to do.