meronymy

Meronymy is a semantic relation between two terms in which one term denotes a part of something that the other term denotes as a whole. The higher-level term is called the holonym; the lower-level term is the meronym. The relation is inherently asymmetrical: a wheel is a meronym of a car, while a car is a holonym of a wheel.

Common subtypes include part meronymy (parts of a whole, such as wheel, door, or engine of a car), member meronymy (a member of a group, such as player of a team), and substance meronymy (a material that constitutes something, such as wood or metal as a substance of a chair). These distinctions help capture different ways in which objects and collections are structurally related.

Meronymy is distinct from hyponymy and hypernymy, which concern subclass and superclass relations (for example, dog is a hyponym of animal). In linguistic resources and NLP, meronymy is used to model part–whole knowledge in lexical databases such as WordNet and to support structure-based reasoning in information retrieval and ontology construction.

Meronymy can intersect with metonymy in language use, where a part or material may be intended to stand for the whole or vice versa in rhetorical contexts. Nonetheless, the meronymic relation is a semantic, rather than purely rhetorical, property of how terms relate to one another.