Incidental

a. [Sp. incidental.]

1. Happening, as an occasional event, without regularity; coming without design; casual; accidental; as, an incidental conversation; an incidental occurrence.
2. Not necessary to the chief purpose; occasional.

By some persons, religious duties appear to be regarded as an incidental business. Rogers. Syn.—Accidental; casual; fortuitous; contingent. See ACCIDENTAL.