conventional (adj.)

late 15c., "of the nature of an agreement," from Late Latin conventionalis "pertaining to convention or agreement," from Latin conventionem "a meeting, assembly, covenant" (see convention). Meaning "of the nature of a convention" in the "formal meeting" sense is from 1812, now rare; that of "established by social convention" is from 1761. Sense of "following tradition" is from 1831; that of "non-nuclear" is from 1955. Related: Conventionality; conventionally.