noun
bacterium
bak-TEERR-eerm
noun
1
A single microscopic organism made of one cell, lacking a nucleus, that belongs to the bacteria group.
"Scientists identified the exact bacterium responsible for the outbreak."
How to Use Bacterium
Learner’s notesIn plain EnglishThe singular form of "bacteria" — one single-celled microbe without a nucleus.
Common mistake
Use "bacterium" for one organism and "bacteria" for more than one — "a bacteria" is a common but technically incorrect usage.
Easily confused with
Word Forms
bacteria plural, bacteriums plural
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Scientists identified the exact _____ responsible for the outbreak.
Etymology
From New Latin bactērium, from the Ancient Greek word for "small staff," referring to the rod-like shape common among these organisms.