The word 零件 is formed through a direct semantic combination of its two characters: 零, which carries the meaning of "fragmentary", "scattered", or "spare part", and 件, meaning an "item" or "component". Together, they conceptually merge to denote a "spare component item", creating the specific idea of an individual, often interchangeable, piece that is part of a larger mechanical or technical assembly. Its formation is based on this straightforward compounding of meanings to define a discrete, fundamental part of a whole system.