bacteria

[bak-teer-ee-uh]
plural noun, singular bacterium [bak-teer-ee-uhm] .
ubiquitous one-celled organisms, spherical, spiral, or rod-shaped and appearing singly or in chains, comprising the Schizomycota, a phylum of the kingdom Monera (in some classification systems the plant class Schizomycetes), various species of which are involved in fermentation, putrefaction, infectious diseases, or nitrogen fixation.

Origin:
1905–10; < Neo-Latin < Greek baktḗria, plural of baktḗrion; see bacterium

bacterial, adjective
bacterially, adverb
nonbacterial, adjective
nonbacterially, adverb
unbacterial, adjective
Dictionary.com Unabridged

bacterium

[bak-teer-ee-uhm] .
noun
singular of bacteria.

Origin:
1840–50; < Neo-Latin < Greek baktḗrion, diminutive of baktēría staff; akin to báktron stick, Latin baculum, bacillum

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Based on the Random House Dictionary, © Random House, Inc. 2014.
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World English Dictionary
bacteria (bækˈtɪərɪə)
 
pl n , sing -rium
See also prokaryote 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
 
[C19: plural of New Latin bacterium, from Greek baktērion, literally: a little stick, from baktron rod, staff]
 
bac'terial
 
adj
 
bac'terially
 
adv

bacterium (bækˈtɪərɪəm)
 
n
the singular of bacteria

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Etymonline
Word Origin & History

bacteria
1847, from Mod.L. pl. of bacterium, from Gk. bakterion "small staff," dim. of baktron "stick, rod," from PIE *bak- "staff used for support." So called because the first ones observed were rod-shaped. Introduced as a scientific word 1838 by Ger. naturalist Christian Gottfried Ehrenberg (1795-1876). Related:
Bacterial (1871).

bacterium
c.1848, sing. of see bacteria (q.v.).
Online Etymology Dictionary, © 2010 Douglas Harper
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American Heritage
Medical Dictionary

bacteria bac·te·ri·a (bāk-tǐr'ē-ə)
n.
Plural of bacterium.


bac·te'ri·al adj.

bacterium bac·te·ri·um (bāk-tēr'ē-əm)
n. pl. bac·te·ri·a (-tēr'ē-ə)
Any of the unicellular, prokaryotic microorganisms of the class Schizomycetes, which vary in terms of morphology, oxygen and nutritional requirements, and motility, and may be free-living, saprophytic, or pathogenic, the latter causing disease in plants or animals.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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American Heritage
Science Dictionary
bacteria   (bāk-tîr'ē-ə)  Pronunciation Key 
Plural of bacterium.
bacterium  [%PREMIUM_LINK%]     (bāk-tîr'ē-əm)  Pronunciation Key 
Plural bacteria
Any of a large group of one-celled organisms that lack a cell nucleus, reproduce by fission or by forming spores, and in some cases cause disease. They are the most abundant lifeforms on Earth, and are found in all living things and in all of the Earth's environments. Bacteria usually live off other organisms. Bacteria make up most of the kingdom of prokaryotes (Monera or Prokaryota), with one group (the archaea or archaebacteria) often classified as a separate kingdom. See also archaeon, prokaryote.

bacterial adjective
Our Living Language  : It is important to remember that bacteria is the plural of bacterium, and that saying a bacteria is incorrect. It is correct to say The soil sample contains millions of bacteria, and Tetanus is caused by a bacterium.

The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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American Heritage
Cultural Dictionary

bacteria definition


sing. bacterium

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

Note: 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).
The American Heritage® New Dictionary of Cultural Literacy, Third Edition
Copyright © 2005 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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Example sentences
Pasteurization is supposed to kill all all the bacteria, good and bad.
Although dozens of Americans have been exposed to the bacteria, so far less
  than 10 people have contracted the disease.
There is a video game in which players fire antibiotic ammunition at bacteria.
Dangerous bacteria could be lurking in the water at the beach.
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