protozoan

American  

[proh-tuh-zoh-uhn] / ˌproʊ təˈzoʊ ən /

noun

• protozoans,
  plural
• protozoa
  plural

1. any of a diverse group of eukaryotes, of the kingdom Protista, that are primarily unicellular, existing singly or aggregating into colonies, are usually nonphotosynthetic, and are often classified further into phyla according to their capacity for and means of motility, as by pseudopods, flagella, or cilia.

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adjective

1. of, relating to, or characteristic of a protozoan.

protozoan British  

/ ˌprəʊtəˈzəʊən /

noun

1. Also called: protozoon. any of various minute unicellular organisms formerly regarded as invertebrates of the phylum Protozoa but now usually classified in certain phyla of protoctists. Protozoans include flagellates, ciliates, sporozoans, amoebas, and foraminifers

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adjective

1. of or relating to protozoans

protozoan Scientific  

/ prō′tə-zō′ən /

• protozoans
  plural

1. Any of a large group of one-celled organisms (called protists) that live in water or as parasites. Many protozoans move about by means of appendages known as cilia or flagella. Protozoans include the amoebas, flagellates, foraminiferans, and ciliates. Their traditional classification as the subkingdom Protozoa is still used for convenience, but it is now known that protozoans represent several evolutionarily distinct groups.

2. See more at protist

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Other Word Forms

Noun Inflected Forms

• protozoa
  plural
• protozoans
  plural

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Etymology

Origin of protozoan

First recorded in 1860–65; Protozo(a) + -an

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Example Sentences

See Examples For:

protozoan protozoa protozoans

Giardia duodenalis is a microscopic protozoan parasite known for causing outbreaks of severe diarrhea.

From Science Daily ● Dec. 21, 2025

A research team placed Halteria ciliates—a type of protozoan with hairlike organelles found in freshwater worldwide—in a petri dish with only chloroviruses, which infect green algae.

From Science Magazine ● Jan. 11, 2023

One common protozoan disease known to occur in birds, which evolved from feathered dinosaurs, as well as in people is called trichomoniasis, caused by a parasitic protozoan.

From Reuters ● Oct. 1, 2022

Though the idea of a mind-altering protozoan transmitted via cats is alarming, it is not necessarily harmful: roughly 30 percent of the human population is infected with the T gondii parasite.

From Salon ● Apr. 19, 2022

Scientists in Czechoslovakia are experimenting with protozoa against webworms and other insect pests, and in the United States a protozoan parasite has been found to reduce the egg- laying potential of the corn borer.

From "Silent Spring" by Rachel Carson

Organisms that can survive in this suspended, or anabiotic, state, Yarzábal explained, include not just extremophile bacteria but also viruses, fungi, protozoa and microscopic animals called nematodes.

From Salon ● Apr. 20, 2025

It seems miraculous that, over billions of years, our planetary circumstances enabled protozoa to evolve into people.

From New York Times ● Nov. 12, 2023

Bottom line: If you must have tropical milkweed, cut it down to the ground each fall before it goes to seed, to kill any overwintering protozoa and reduce its potential to spread to neighboring areas.

From Los Angeles Times ● Oct. 30, 2023

Food turns into compost through the hard work of small microorganisms like bacteria, fungi, and protozoa.

From National Geographic ● Sep. 26, 2023

Far from recognizing that protozoa were different in character from larger organisms, Leeuwenhoek’s work seemed to imply that they were the same.

From "The Invention of Science" by David Wootton

The researchers explored whether the holes had been caused by an infection involving microbes called protozoans.

From Reuters ● Oct. 1, 2022

The broadest definition of “parasite” includes pathogens such as bacteria, viruses, fungi and protozoans.

From Scientific American ● May 18, 2022

His companion guide to garden science is a learned romp through plant biology; solar energy and soil nutrients; the movement of vines; and “fellow gardeners”, from single-celled protozoans to beetles.

From Nature ● Mar. 20, 2018

And just like a tapeworm or malaria protozoans, it doesn’t care if it disables or kills its host.

From Slate ● Mar. 29, 2017

The scoutmaster had given them a long lecture about disrupting nature—by the end of it, Jonah felt guilty about how many protozoans he’d probably killed.

From "Found" by Margaret Peterson Haddix

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