noun Uncommon

bacterium

bak-TEERR-eerm

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Bacterium (noun) means a single microscopic organism made of one cell, lacking a nucleus, that belongs to the bacteria group. Example: “Scientists identified the exact bacterium responsible for the outbreak.”

noun

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 notes

In 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

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C2 · Advanced serendipity Fortunate discoveries made entirely by accident.

Gen Z slang rizz Charm — the ability to attract a romantic interest.

B2 · Intermediate empathy The capacity to share another person’s feelings.

C1 · Advanced nonchalant Casually calm and relaxed; unconcerned.

Internet slang delulu Delusional — believing something against the odds.

Etymology nostalgia Greek nostos “return home” + algos “pain”.

C2 · Advanced serendipity Fortunate discoveries made entirely by accident.

Gen Z slang rizz Charm — the ability to attract a romantic interest.

B2 · Intermediate empathy The capacity to share another person’s feelings.

C1 · Advanced nonchalant Casually calm and relaxed; unconcerned.

Internet slang delulu Delusional — believing something against the odds.

Etymology nostalgia Greek nostos “return home” + algos “pain”.

Word forms

Plural: bacteria, bacteriums

Test yourself on “bacterium” A quick quiz — meaning, synonyms & usage →

Fill the gap

Can you complete this real example?

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.

Origin: Ancient Greek

Synonyms

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bacteria

Related words

bacteria germ

Rhymes for bacterium

curium osmium cerium erbium sodium helium cadmium caesium fermium gallium niobium thulium

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Frequently asked questions

What does “bacterium” mean?

The word “bacterium” means a single microscopic organism made of one cell, lacking a nucleus, that belongs to the bacteria group. In plain terms, the singular form of "bacteria" — one single-celled microbe without a nucleus.

How do you pronounce “bacterium”?

“Bacterium” is pronounced bak-TEERR-eerm (/bækˈtɪəɹ.ɪəm/ in IPA).

How do you use “bacterium” in a sentence?

Here is “bacterium” used in a sentence: “Scientists identified the exact bacterium responsible for the outbreak.”

What part of speech is “bacterium”?

“Bacterium” is a noun.

Where does the word “bacterium” come from?

The word “bacterium” comes from Ancient Greek. From New Latin bactērium, from the Ancient Greek word for "small staff," referring to the rod-like shape common among these organisms.

Is “bacterium” a common word?

“Bacterium” is an uncommon word in modern English.

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