Meronymy and holonymy
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In linguistics, meronymy (from Greek μέρος, méros, "part", and ὄνυμα, ónuma, "name") is a semantic relation between a meronym denoting a part and a holonym denoting a whole. In simpler terms, a meronym is in a part-of relationship with its holonym. For example, finger is a meronym of hand which is its holonym. Similarly, engine is a meronym of car which is its holonym.
Holonymy (from Greek ὅλος, hólos, "whole", and ὄνυμα, ónuma, "name") is the converse of meronymy.
A closely related concept is that of mereology, which specifically deals with part–whole relations and is used in logic. It is formally expressed in terms of first-order logic. A meronymy can also be considered a partial order.
A meronym refers to a part. A hyponym refers to a type. For example, a meronym of tree is bark or leaf (a part of tree), but a hyponym of tree is pine tree or oak tree (a type of tree).