Definition

A parasite is an organism that lives in intimate association with another organism on which it depends for its nutrition; not necessarily a pathogen (adjective parasitic).

Etymology. 1539, "a hanger-on, a toady, "person who lives on others," from M.Fr. parasite, from L. parasitus, from Gk. parasitos "person who eats at the table of another," from n. use of adj. meaning "feeding beside," from para- "beside" + sitos "food," of unknown origin. Scientific meaning "animal or plant that lives on others" is first recorded 1646 (implied in parasitical).