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.

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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

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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

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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

"You see the rise of mobility, predation, and, clearly, parasitism."

From Science Daily • Nov. 5, 2025

“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

Among ants, social parasitism has evolved about 91 times, he points out.

From Science Magazine • Mar. 5, 2023

Maria did not realize until later in her life that these “false changes”—moth cocoons that produced flies or wasps instead of moths—were caused by insect parasitism.

From "The Girl Who Drew Butterflies: How Maria Merian's Art Changed Science" by Joyce Sidman