parasite
UK: ˈpærəsaɪt | US: ˈpærəsaɪt
n. an organism that lives on or in another organism (its host) and benefits by deriving nutrients at the host's expense
n. a person who habitually relies on or exploits others without giving anything in return
The word "parasite" originates from Greek parasitos, combining para- (beside) and sitos (food, grain). Originally, it referred to a person who ate at another's table (a "dinner guest" in ancient Greek society), often implying someone who flattered the host for free meals. Over time, the term evolved biologically to describe organisms that live off hosts, retaining the core idea of one-sided benefit. The morpheme para- appears in many English words (e.g., "parallel," "paradox"), while site is rare outside this context.
The flea is a common parasite that feeds on the blood of mammals.
She accused her lazy roommate of being a parasite who never contributed to rent.
Some fungi act as parasites, weakening their host plants.
The documentary exposed corrupt officials as parasites draining public funds.
In nature, parasites often evolve to avoid killing their hosts too quickly.