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."
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Three doctors gathered and told the couple that the longer Waldorf’s cervix remained open and her uterus exposed to bacteria, the higher her risk of developing a life-threatening infection.
From Salon • May 27, 2026
Certain bacteria in the mouth help convert nitrate from food into compounds that eventually support the production of nitric oxide.
From Science Daily • May 25, 2026
Restarted weekly tests to determine the quality of Jersey's seawater have identified "unacceptable levels of bacteria in seawater" in some spots.
From BBC • May 25, 2026
Of course, not all shipwrecks find themselves in such relatively hospitable conditions—the Titanic, for instance, is slowly being gobbled up by iron-eating bacteria.
From The Wall Street Journal • May 22, 2026
These, under high magnification, turn out to be bacteria, living in symbiosis with the spirochetes and the protozoan, probably contributing enzymes that break down the cellulose.
From "The Lives of a Cell" by Lewis Thomas
Definitions 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.
