A meronomy or partonomy is a type of hierarchy that deals with part–whole relationships, in contrast to a taxonomy whose categorisation is based on discrete sets. These conceptual structures are used in linguistics and computer science, with applications in biology. The part–whole relationship is sometimes referred to as HAS-A, and corresponds to object composition in object-oriented programming. The study of meronomy is known as mereology, and in linguistics a meronym is the name given to a constituent part of, the substance of, or a member of something. "X" is a meronym of "Y" if an X is a part of a Y.