Plural word for bacteria Bacteria is the plural form of the singular bacterium. Because microscopic bacterium is most often found in multiples, the plural form bacteria is more commonly used. The plurals of several other singular words ending in -um are also formed this way, such as memorandum/memoranda and curriculum/curricula. The irregular noun bacterium’s plural derives directly from its original pluralization in Latin and Greek. Bacteria is sometimes treated as a singular collective noun. However, this is not standard in English, and bacteria should be treated as a plural form.
Some bacteria are beneficial to humans (for example, those that live in the stomach and aid digestion), and some are harmful (for example, those that cause disease).
First recorded in 1860–65; from New Latin, from Greek baktḗria, plural of baktḗrion, diminutive of baktēría “staff, cane”; see origin at bacterium
First recorded in 1860–65; from New Latin; see origin at bacteria ( def. )
Bacteria are microscopic living organisms, usually one-celled, that can be found everywhere. They can be dangerous, such as when they cause infection, or beneficial, as in the process of fermentation (such as in wine) and that of decomposition. In 1676, Anton Van Leeuwenhoek first observed bacteria through a microscope and called them “animalcules.” In 1838, the German Naturalist Christian Gottfried Ehrenberg called them bacteria, from the Greek baktḗria, meaning "little stick." An apt word, as the first observed bacteria were shaped like rods, although bacteria can also be spiral or spherical in shape. A grammar note: The word bacteria is the plural form of "bacterium" and so should be written as plural, as in "Many bacteria are harmless."
Looking to grow your vocabulary? Check out this interactive, curated word list from our team of English language specialists at Vocabulary.com – one of over 17,000 lists we've built to help learners worldwide!
Interested in learning more words like this one? Our team at Vocabulary.com has got you covered! You can review flashcards, quiz yourself, practice spelling, and more – and it's all completely free to use!
Want to remember this word for good? Start your learning journey today with our library of interactive, themed word lists built by the experts at Vocabulary.com – we'll help you make the most of your study time!
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
Some polymers contain bonds that microbial enzymes can attack, allowing bacteria to dismantle them into smaller molecules.
From Science Daily ● Oct. 16, 2026
This sleight of hand, Mr. Silvertown explains, was first performed by aquatic bacteria more than three billion years ago.
From The Wall Street Journal ● Oct. 16, 2026
The Pac-Man enzyme illustrates how bacteria can exploit these molecular weak points, offering new insight into the relationship between plastic pollution, microbial adaptation, and the future of biodegradable materials.
From Science Daily ● Oct. 16, 2026
Then about 1.25 billion years ago, one of these photosynthesizing bacteria partnered with another one-celled organism to create green algae, one lineage of which became the ancestor of all plants.
From The Wall Street Journal ● Oct. 16, 2026
But when he mixed the dead material from the virulent strain with live bacteria of the nonvirulent strain, the mice died rapidly.
From "The Gene" by Siddhartha Mukherjee
Bacteria in treated trees have dropped by at least 90%.
From The Wall Street Journal ● Sep. 19, 2026
Bacteria found in soil and water are essential parts of natural ecosystems, and some species are capable of processing substances that can be harmful to humans and other organisms.
From Science Daily ● Aug. 9, 2026
Bacteria that survive a drug can reproduce and pass their resistance to future generations.
From Science Daily ● Jul. 22, 2026
Bacteria can also infect wounds where screwworm maggots are present and may cause an infection that can lead to symptoms like fever or chills.
From Los Angeles Times ● Jun. 6, 2026
Bacteria have a lot more to do than viruses.
From "Cosmos" by Carl Sagan
Plague is a disease caused by the Yersinia pestis bacterium, the same pathogen that killed millions of people in Europe during the Middle Ages.
From Barron's ● Oct. 7, 2026
The bacterium that causes the plague, Yersinia pestis, found among rodents such as marmots in the area.
From BBC ● Oct. 7, 2026
The bacterium Yersinia pestis, which can cause pneumonic and bubonic plague, has been identified from time to time in Siberia, linked to exposure to vermin.
From The Wall Street Journal ● Oct. 6, 2026
Instead, the disease appears to have resurfaced in different parts of Europe over hundreds of years, potentially creating several new reservoirs where the bacterium could persist.
From Science Daily ● Sep. 20, 2026
Bruno Latour maintained that the fact that the bacterium that causes tuberculosis has been discovered in the lungs of an ancient Egyptian pharaoh, Ramses II, did not mean that Ramses died of tuberculosis.
From "The Invention of Science" by David Wootton
Spin the wheel and learn a new word!
Get a wordDefinitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
