parasite

/ˈpɛrəˌsaɪt/

an animal or plant that lives in or on a host (another animal or plant); it obtains nourishment from the host without benefiting or killing the host

中文释义：寄生虫；寄生生物

The tapeworm is a common parasite that lives in the intestines of mammals.

绦虫是一种常见的寄生在哺乳动物肠道内的寄生虫。

Some parasites can cause serious diseases in their hosts if left untreated.

如果不治疗，一些寄生虫会在宿主体内引起严重疾病。