parasite
/ˈpærəsaɪt/noun
1- an organism which lives in or on another organism (its host) and benefits by deriving nutrients at the other's expense寄生生物; 寄生植物。
1.1
- derogatory a person who habitually relies on or exploits others and gives nothing in return〈贬〉过着寄生生活的人, 寄生虫。
Parasites exist in huge variety, including animals, plants, and micro-organisms. They may live as exoparasites on the surface of the host （e.g. arthropods such as ticks, mites, lice, fleas, and many insects infesting plants） or as endoparasites in the gut or tissues （e.g. many kinds of worm）, and cause varying degrees of damage or disease to the host.
词源
mid 16th cent.: via Latin from Greek parasitos '(person) eating at another's table', from para- 'alongside' + sitos 'food'.