Hyponymy

In linguistics, a hyponym is a word or phrase whose semantic field is included within that of another word, its hypernym (sometimes spelled hyperonym outside of the natural language processing community). In simpler terms, a hyponym shares a type-of relationship with its hypernym. For example, scarlet, vermilion, carmine, and crimson are all hyponyms of red (their hypernym), which is, in turn, a hyponym of colour.

Hypernymy is the semantic relation in which one word is the hypernym of another. Hypernymy, the relation in which words stand when their extensions stand in the relation of class to subclass, should not be confused with holonymy, which is the relation in which words stand when the things that they denote stand in the relation of whole to part. A similar warning applies to hyponymy and meronymy.

As a hypernym can be understood as a more general word than its hyponym, the relation is used in semantic compression by generalization to reduce a level of specialization.

Research
In the case of hyponymy, psychological experiments revealed that individuals can access properties of nouns more quickly depending on when a characteristic becomes a defining property. That is, individuals can quickly verify that canaries can sing because a canary is a songbird (only one level of hyponymy), but requires slightly more time to verify that canaries can fly (two levels of hyponymy) and even more time to verify canaries have skin (multiple levels of hyponymy). This suggests that we too store semantic information in a way that is much like WordNet, because we only retain the most specific information needed to differentiate one particular concept from similar concepts.