bacteria

noun

bac·​te·​ria bak-ˈtir-ē-ə 

plural of bacterium

diseases caused by bacteria

Overprescribing antibiotics can contribute to the development of antibiotic-resistant bacteria.

—Maanvi Singh

Note: Microscopic single-celled organisms lacking a distinct nucleus are known as bacteria. They may be shaped like spheres, rods, or spirals. They inhabit virtually all environments, including soil, water, organic matter, and the bodies of animals. Many bacteria swim by means of long whiplike structures called flagella. The DNA of most bacteria is found in a single, circular chromosome, and is distributed throughout the cytoplasm rather than contained within a membrane-enclosed nucleus. Though some bacteria can cause food poisoning and infectious diseases in humans, most are harmless and many are beneficial. They are used in various industrial processes, especially in the food industry (for example, in the production of yogurt, cheeses, and pickles).

About Viruses and Bacteria: Usage Guide

Viruses differ from bacteria in several important ways. Viruses are not living organisms; they can only replicate in the cells of a host. By contrast, bacteria are single-celled organisms that can reproduce on their own and are many times larger than viruses. While both viruses and bacteria can cause disease, most bacteria are harmless and many are beneficial.

Examples of bacteria in a Sentence

Recent Examples on the Web

Pluralibacter gergoviae is a bacteria that has been linked to respiratory diseases, urinary tract infections, eye infections and sepsis, particularly in immunocompromised people, according to Melbec Microbiology, a microbiology testing company that specializes in cosmetics. —Toria Sheffield, PEOPLE, 26 Oct. 2025

Urinary Tract Infection A urinary tract infection (UTI) occurs when bacteria enter the urinary tract, causing infection and inflammation. —Lindsay Curtis, Health, 25 Oct. 2025

The system works in bacteria, human cells, and even live tumor models, offering a safer and more precise alternative to traditional techniques. —Neetika Walter, Interesting Engineering, 24 Oct. 2025

The oxidation of your pumpkin’s insides can mean that mold and bacteria begin to form on that inner flesh that is no longer protected after the thick skin of the gourd is compromised through carving. —Patricia Shannon, Southern Living, 24 Oct. 2025

Word History

Etymology

plural of bacterium

First Known Use

1864, in the meaning defined above

Rhymes for bacteria

• arteria
• criteria
• diphtheria
• egeria
• listeria
• neisseria
• wisteria
• cafeteria
• cyanobacteria
• mycobacteria

Kids Definition

bacteria

plural of bacterium

Medical Definition

bacteria

1 of 2

plural of bacterium

bacteria

2 of 2 noun

bac·​te·​ria bak-ˈtir-ē-ə 

1

: bacterium

—not usually used technically

caused by a bacteria borne by certain tiny ticks

—Wall Street Journal

a single bacteria—there are roughly 200 in each cough—apparently can infect a person

—Cheryl Clark

2

plural capitalized : a domain in the system of classification dividing all organisms into three major domains of life that includes the prokaryotes that are bacteria but not those that are archaea compare eubacteria