The Collaborative International Dictionary of English v.0.48:
hyponymy \hyponymy\ n. (Linguistics) The state or quality of being a hyponym; as, hyponymy is symbolized by the tag "hypon". [PJC]WordNet (r) 3.0 (2006):
hyponymy n 1: the semantic relation of being subordinate or belonging to a lower rank or class [syn: hyponymy, subordination]