View synonyms for bacteria



[ bak-teer-ee-uh ]

plural noun

, Microbiology.
, singular bac·te·ri·um [bak-, teer, -ee-, uh, m].
  1. ubiquitous one-celled organisms, spherical, spiral, or rod-shaped and appearing singly or in chains, comprising numerous and variously classified phyla: among the inestimable number of species are those involved in fermentation, putrefaction, infectious diseases, and nitrogen fixation.



[ bak-teer-ee-uh ]


, (used with a singular or plural verb)
  1. (in the three-domain system of classification) the taxonomic domain comprising the bacteria.


/ bækˈtɪərɪə /

plural noun

  1. a very large group of microorganisms comprising one of the three domains of living organisms. They are prokaryotic, unicellular, and either free-living in soil or water or parasites of plants or animals See also prokaryote


  1. sing. bacterium Microorganisms made up of a single cell that has no distinct nucleus . Bacteria reproduce by fission or by forming spores .

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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).

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Derived Forms

  • bacˈterial, adjective
  • bacˈterially, adverb

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Other Words From

  • bac·teri·al adjective
  • bac·teri·al·ly adverb
  • nonbac·teri·al adjective
  • nonbac·teri·al·ly adverb

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Word History and Origins

Origin of bacteria1

First recorded in 1860–65; from New Latin, from Greek baktḗria, plural of baktḗrion, diminutive of baktēría “staff, cane”; bacterium

Origin of bacteria2

First recorded in 1860–65; from New Latin; bacteria ( def )

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Word History and Origins

Origin of bacteria1

C19: plural of New Latin bacterium , from Greek baktērion , literally: a little stick, from baktron rod, staff

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Example Sentences

The more antibiotics are used inappropriately, the greater the risk of bacteria growing resistant to them.

What specific bacteria and viruses can be detected in the sewage?

If all animals vanished, most bacteria would still live on, but if all bacteria disappeared, we would die quickly.

A new book focuses on gut bacteria as the key to a healthy weight.

But consider that when we eat, the bacteria are actually fed first.

Bacteria, when present in great numbers, give a uniform cloud which cannot be removed by ordinary filtration.

It is to be remembered, however, that a few of these bacteria may reach the sputum from the upper air-passages.

Bacteria of various kinds, especially staphylococci, are usually numerous.

They are able to migrate readily from place to place and to ingest small bodies, as bacteria.

Undiluted normal blood can agglutinate most bacteria, but loses this power when diluted to any considerable degree.


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What Is The Plural Of Bacteria?

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.

More About Bacteria

What is bacteria?

Bacteria is a collective name for a large number of single-celled, microscopic organisms that live in the soil, water, or animals, including humans. They come in several different shapes, including spheres, rods, and spirals, and may organize themselves into clusters or chains.

Bacteria consist of only a single cell. Additionally, bacteria are prokaryotes, which means their single cell does not have a nucleus like an animal or plant cell does. Instead, their genetic material (DNA) just floats around inside the cell. Bacteria often have a single loop of DNA and possibly some other genes they have picked up in the environment.

Bacteria reproduce by what is known as binary fission. A single bacteria splits itself into two identical copies (clones) of the original, meaning the two “children” have the exact same genetic material as the “parent.” Bacteria can often become immune to antibiotics quickly because they never lose any genes they have picked up that help them survive. Bacteria can reproduce extraordinarily fast under the right conditions with a single bacteria making millions of copies of itself in just a few hours.

Bacteria are incredibly common in nature and live in almost every environment on Earth. Most bacteria are harmless or help out other organisms in some way. For example, there are several kinds of bacteria that live in the human intestines that help breakdown foods or assist in warding off disease-causing organisms.

The singular of bacteria is bacterium.

Bacteria are often confused with another disease-causing microscopic organism known as a virus. Unlike bacteria, viruses cannot reproduce on their own. Instead, they infect other cells and force them to make copies of the virus. Because of their often destructive reproductive method, viruses are typically seen as harmful parasites, and there are far fewer examples of helpful viruses than helpful bacteria.

Why is bacteria important?

The first records of the word bacteria come from around 1860. It ultimately comes from the Greek word baktḗria, meaning “little canes” or “little sticks.” Some bacteria resemble sticks or rods, while others have different shapes. Bacteria are found everywhere on Earth and have been found in fossils that are hundreds of millions of years old. Scientists have argued that bacteria first appeared on Earth around 3.5 billion years ago, while humans have only been around for about 200,000 years.

Besides helping us and other animals digest food, bacteria have other beneficial uses. Several kinds of bacteria are essential to making yogurt, buttermilk, and cheese. Bacteria are also used to make different kinds of alcohol and to make vinegar.

Some bacteria, such as certain species of E. Coli, cause disease in animals and plants. This is a result of the bacteria releasing or secreting toxic chemicals that cause damage to the cells or tissues and result in diseases such as tetanus or cholera. While the immune system tries to kill most bacteria by itself, humans have developed medicines known as antibiotics that are designed to kill bacteria.

Did you know … ?

Your body is actually made up of ten times as many bacteria cells as human cells! Bacteria live both inside you, as well as all over your skin. However, their small size means they only make up about 1 percent of total body mass.

What are real-life examples of bacteria?

This image shows a zoomed-in photo of a species of bacteria known as Clostridioides difficile, which causes diarrhea in humans.

Many people are most familiar with bacteria from the “bad eggs” that cause disease in humans.

What other words are related to bacteria?

Quiz yourself!

True or False?

Bacteria only have a single cell.




bacteri-bacteria bed