What does entozoon mean?
An entozoon (plural: entozoa) is an animal that lives as a parasite inside the body of another organism — most commonly a worm such as a tapeworm, roundworm, or fluke dwelling in the intestines or other internal organs of its host. The term derives from Greek roots meaning 'within' and 'animal,' and entered English scientific vocabulary in the nineteenth century, when naturalists catalogued the internal parasites of humans and domesticated animals under the collective heading Entozoa. Today the word survives mainly in zoological and historical-medical writing, having been largely displaced by the broader modern term 'endoparasite,' which also covers internal protozoa and other non-worm parasites. Its adjective forms are 'entozoic' and 'entozoal.' Though rarely heard outside specialist contexts, it remains a precise and evocative label for the hidden animal inhabitants of a living body, and it pairs naturally with discussions of infestation, host organisms, and veterinary pathology.
nounAn animal that lives as a parasite inside the body of another animal; an internal parasite, especially a helminth such as a roundworm or tapeworm.
- An animal parasite that inhabits the interior of its host's body, especially a parasitic worm such as a tapeworm or roundworm.
"The veterinarian explained that the lamb's poor condition was caused by entozoa in its digestive tract."
"Microscopic examination of the specimen revealed numerous entozoa embedded in the intestinal wall."
"Nineteenth-century zoologists devoted entire monographs to classifying the entozoa of domestic livestock."
The plural follows the Greek neuter second-declension pattern (-on → -a), like 'criterion' → 'criteria.' In practice, 'entozoa' is encountered more often than the singular, since writers typically refer to these parasites collectively.
"Livestock grazing on contaminated pastures are prone to heavy burdens of entozoa."
Coined from Greek roots meaning 'animal within,' this 19th-century scientific term literally names the worms hiding inside you.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of entozoon
The word entozoon comes from the Greek prefix 'ento-' meaning 'within' and 'zōion' meaning 'animal,' so it literally means 'an animal within.' It was adopted into English scientific nomenclature during the nineteenth century, when zoologists grouped internal parasites — chiefly parasitic worms — under the collective category Entozoa, contrasted with Ectozoa, the external parasites. It shares the same Greek root 'zōion' with words such as 'protozoan' and 'zodiac,' while its prefix connects it to terms like 'endogenous.'
Related word forms
How entozoon is actually used
A technical term used chiefly in zoology and older medical literature; it has largely been superseded in modern usage by 'endoparasite.' The plural 'entozoa' follows Greek declension and is far more frequently encountered than the singular. The word carries no figurative or informal use.
Easily confused with entozoon
An ectozoon is a parasite that lives on the outside of its host's body, whereas an entozoon lives inside.
An epizoon is any organism living on the surface of another animal, not necessarily parasitic, while an entozoon is specifically an internal parasite.