The pinworm (species Enterobius vermicularis), also known as threadworm (in the United Kingdom and Australasia) or seatworm, is a parasitic worm. It is a nematode (roundworm) and a common intestinal parasite or helminth, especially in humans. The medical condition associated with pinworm infestation is known as enterobiasis (a type of helminthiasis) or less precisely as oxyuriasis in reference to the family Oxyuridae.