parasitism

noun

par·​a·​sit·​ism ˈper-ə-sə-ˌti-zəm 

-ˌsī-,

ˈpa-rə-

1

: the behavior of a parasite

2

: an intimate association between organisms of two or more kinds

especially : one in which a parasite obtains benefits from a host which it usually injures

3

: parasitosis

Examples of parasitism in a Sentence

Recent Examples on the Web

Evidence of shifts in sleep and rest in birds and bats has been shown to happen when there is a risk of parasitism after dark. —Elizabeth Rayne, ArsTechnica, 2 May 2025

Female birds actually can manage a free lunch through brood parasitism by forcing other birds to raise their hatchlings. —Nathan H. Lents, Smithsonian Magazine, 11 Apr. 2025

Most species practice intraspecific brood parasitism, which is the laying of eggs in the nests of other birds of the same species. —Nathan H. Lents, Smithsonian Magazine, 11 Apr. 2025

In some orchids, photosynthesis is out and parasitism is in. —Laura Baisas, Popular Science, 19 Feb. 2025

Word History

First Known Use

circa 1611, in the meaning defined at sense 1

Kids Definition

parasitism

noun

par·​a·​sit·​ism ˈpar-ə-sə-ˌtiz-əm 

-ˌsīt-ˌiz-

: a close association between living things of two or more kinds of which one is a parasite obtaining benefits from the other which is a host and is usually harmed in some way

Medical Definition

parasitism

noun

par·​a·​sit·​ism ˈpar-ə-sə-ˌtiz-əm  -ˌsīt-ˌiz- 

1

: an intimate association between organisms of two or more kinds

especially : one in which a parasite obtains benefits from a host which it usually injures

2

: parasitosis