Parasitism
noun /ˈpær.ə.sɪ.tɪ.z(ə)m/ — A relationship where one organism benefits at another's expense.
Definition
A relationship between two organisms in which one (the parasite) benefits at the expense of the other (the host). Parasites typically do not kill their hosts immediately — they depend on them remaining alive. This is the relationship's dark logic.
Beyond the definition
Parasitism is one of biology's most instructive metaphors. The parasite needs the host to survive — which means the perfectly successful parasite is invisible and self-limiting. Too much harm and you destroy your source. The unseen burden.
Origin & history
Greek: 'parasitos' (one who eats at another's table). From 'para' (alongside) + 'sitos' (food). The original Greek word was not negative — it described someone who ate at another's expense by providing entertainment.
Example sentences
Illustrative sentences for learning, not verified community posts or sourced quotations.
The relationship had become parasitic — she was giving everything and receiving nothing.
The tapeworm is a masterclass in parasitism: invisible, efficient, rarely fatal to the host.
Certain business models are parasitic on existing cultural production without contributing to it.
Synonyms
exploitation, leeching, dependence
Antonyms
Related words
Parasitism vs mutualism
Parasitism is an exploitative relationship. Mutualism is a cooperative relationship where everyone involved gains an advantage.
Compare this word
Word in the Wild
See how this word appears in life, language and stories.
Illustrative sentences and imagined stories for learning — not verified sightings, interviews, or sourced quotations.
Illustrative example
Hyenas Surrounding A Single Lioness
Three spotted hyenas surround a lone lioness in dry grassland, their bodies oriented toward her in a tension-filled, confrontational, predatory encounter.
This scene models parasitism, where the hyenas depend on the lioness's success to thrive. They do not kill her immediately, but rely on her active role to secure the resources they exploit, illustrating the dark logic where one depends on the other's continued energy to live.
Image credit: Brittany Gunther · CC BY-SA 4.0 (license)
Uses the source's first cropped frame; resized and converted to WebP.