BACTERIUM

bacteria, bacterium

(noun) (microbiology) single-celled or noncellular spherical or spiral or rod-shaped organisms lacking chlorophyll that reproduce by fission; important as pathogens and for biochemical properties; taxonomy is difficult; often considered to be plants

Source: WordNet® 3.1

Etymology

Noun

bacterium (plural bacteria)

(microbiology) A single celled organism with cell walls but no nucleus or organelles.

Usage notes

• In most formal writing, bacterium is the singular form of the noun, and bacteria the plural form. This is in accord with the word's Latin etymology. However, in ordinary speech, some speakers use bacteria as a singular, with plural either bacteria or bacterias. This is usually considered nonstandard.

Hypernyms

• prokaryote

Hyponyms

• See also bacterium

Source: Wiktionary

Bac*te"ri*um, n.; pl. Bacteria. Etym: [NL., fr. Gr., , a staff: cf. F. bactérie. ] (Biol.)

Definition: A microscopic vegetable organism, belonging to the class Algæ, usually in the form of a jointed rodlike filament, and found in putrefying organic infusions. Bacteria are destitute of chlorophyll, and are the smallest of microscopic organisms. They are very widely diffused in nature, and multiply with marvelous rapidity, both by fission and by spores. Certain species are active agents in fermentation, while others appear to be the cause of certain infectious diseases. See Bacillus.

Source: Webster’s Unabridged Dictionary 1913 Edition