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.
Cooling systems can draw large volumes of municipal water, while mists from cooling towers can carry harmful bacteria.
From Barron's ● Nov. 5, 2026
A virus capable of killing one strain of bacteria may have little or no effect on another.
From Science Daily ● Nov. 5, 2026
Before treatment begins, specialists must therefore determine whether a particular phage can successfully attack the bacteria responsible for a patient's infection.
From Science Daily ● Nov. 5, 2026
The thousands of valves being replaced showed "accelerated deterioration due to the existing chemical dosage regime" being used to flush out any bacteria, it said.
From BBC ● Nov. 4, 2026
A cut or break in the skin lets staph and strep bacteria colonize the warm, wet, nutrient-rich cells inside.
From "Phineas Gage" by John Fleischman
Bacteria in treated trees have dropped by at least 90%.
From The Wall Street Journal ● Sep. 19, 2026
Bacteria and viruses can hide inside amoebae, where they may be shielded from disinfectants and other treatment methods.
From Science Daily ● Jun. 6, 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 and viruses can survive inside amoebae, shielded from disinfection processes that would normally eliminate them.
From Science Daily ● Jan. 25, 2026
Bacteria, fungi, and algae are the principal agents of decay, reducing plant and animal residues to their component minerals.
From "Silent Spring" by Rachel Carson
Because they are all “kissing cousins,” as Livieri puts it, they fail to express a protein that helps fight the bacterium behind the medieval Black Death.
From The Wall Street Journal ● Nov. 4, 2026
Instead of preventing an existing toxin from causing harm, it helps turn on toxin production only when the bacterium detects a threat.
From Science Daily ● Oct. 31, 2026
The bacterium that causes it still exists in parts of Africa and Asia, including Siberia.
From The Wall Street Journal ● Oct. 30, 2026
The bacterium that causes the plague, Yersinia pestis, found among rodents such as marmots in the area.
From BBC ● Oct. 7, 2026
How could heat-killed bacterial debris—no more than a lukewarm soup of microbial chemicals—have transmitted a genetic trait to a live bacterium by mere contact?
From "The Gene" by Siddhartha Mukherjee
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.
