In linguistics, meronymy (from Ancient 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.
Fellow meronyms (naming the various fellow parts of any particular whole) are called comeronyms (for example, leaves, branches, trunk, and roots are comeronyms under the holonym of tree).
Holonymy (from Ancient Greek ὅλος (hólos) 'whole' and ὄνυμα (ónuma) 'name') is the converse of meronymy.
It is formally expressed in terms of first-order logic.