A meronomy or partonomy is a type of hierarchy that deals with part–whole relationships, in contrast to a taxonomy whose categorisation is based on discrete sets. Accordingly, the unit of meronomical classification is meron, while the unit of taxonomical classification is taxon. These conceptual structures are used in linguistics and computer science, with applications in biology. The part–whole relationship is sometimes referred to as HAS-A, and corresponds to object composition in object-oriented programming. The study of meronomy is known as mereology, and in linguistics a meronym is the name given to a constituent part of, the substance of, or a member of something. "X" is a meronym of "Y" if an X is a part of a Y.
- Cars have parts: engine, headlight, wheel
- Engines have parts: crankcase, carburetor
- Headlights have parts: headlight bulb, reflector
In knowledge representation
- Transitive – "Parts of parts are parts of the whole" – if A is part of B and B is part of C, then A is part of C.
- Reflexive – "Everything is part of itself" – A is part of A.
- Antisymmetric – "Nothing is a part of its parts" – if A is part of B and A ≠ B then B is not part of A.