Origin: Greek prefix para-
Parasite has 3 different meanings across 1 category:
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
"The tick climbed onto my dog's fur to feed on its blood, acting as a parasite while leaving the animal otherwise unharmed."
A person who lives on other people's efforts or expense and gives little or nothing back.
"My roommate is a total parasite because he never pays his share of the rent but expects to eat all our meals for free."