parasitism

American  

[par-uh-sahy-tiz-uhm, -si-] / ˈpær ə saɪˌtɪz əm, -sɪ- /

noun

1. Biology. a relation between organisms in which one lives as a parasite on another.

2. a parasitic mode of life or existence.

3. Pathology. a diseased condition due to parasites.

4. (in some totalitarian countries)

   1. unemployment or refusal to work.

   2. employment in work considered nonessential by the state.

---

parasitism British  

/ ˈpærəsaɪˌtɪzəm /

noun

1. the relationship between a parasite and its host

2. the state of being infested with parasites

3. the state of being a parasite

---

parasitism Scientific  

/ păr′ə-sĭ-tĭz′əm /

1. A relationship between two organisms in which one organism (the parasite) benefits and the other (the host) is harmed. Parasites derive nutrition from their host and may also gain other benefits such as shelter and a habitat in which to grow and reproduce.

2. See more at parasite Compare amensalism commensalism mutualism

---

Other Word Forms

• nonparasitism
  noun

Etymology

Origin of parasitism

First recorded in 1605–15; parasite + -ism

Explanation

Parasitism is a relationship between two things in which one of them (the parasite) benefits from or lives off of the other, like fleas on your dog. Parasitism and its root, parasite, come from para-, meaning "beside" or "next to," and sito, meaning "bread or food." There is parasitism in plant life, like the kudzu vine that grows on trees. We also talk about social parasitism, when someone lives at the expense of someone else. Some people think that government programs such as welfare or corporate grants and tax breaks are a form of parasitism.

Example Sentences

See Examples For:

parasitism

Joseph Brodsky, who later won the Nobel Prize for literature, was charged with parasitism when he spent his days writing verse.

From The Wall Street Journal ● Jul. 10, 2026

Members of the vertebrate group including anglerfishes are unique in possessing a characteristic known as sexual parasitism, in which males temporarily attach or permanently fuse with females to mate.

From Science Daily ● May 23, 2024

“When you add this significant stressor of parasitism to the equation, I think it's a perfect storm,” she says.

From National Geographic ● Feb. 15, 2024

There’s a biological phenomenon known as parasitism, a relationship in which a parasite benefits while its host is harmed.

From Seattle Times ● Aug. 4, 2023

And there are many wasps, and flies as well, whose very existence depends on the destruction of the eggs or larvae of other insects through parasitism.

From "Silent Spring" by Rachel Carson