Bacteria or bacterium?
bacteria is the plural of bacterium. In written English (wordfreq, 2021 data) bacteria is about 14 times as common as bacterium.
What is the difference between bacteria and bacterium?
| bacteria | bacterium | |
|---|---|---|
| Part of speech | noun | noun |
| Meaning | plural of bacterium USA type, species, or strain of bacterium | A single-celled organism with cell walls but no nucleus or organelles |
| Example | none recorded | none recorded |
| Forms | bacterias bacteriae | bacteria |
| Pronunciation | /bakˈtɪə̯.ri.ə/ /bækˈtɪɹ.i.ə/ | /bækˈtɪəɹ.ɪəm/ |
| In writing | 15 times per million words | 1.1 times per million words |
Sources: bacteria and bacterium in the English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0); written frequency: wordfreq 3.1 (a 2021 snapshot of Wikipedia, subtitles, news, books, web text and social media).
Every current meaning of bacteria and bacterium
bacteria
- 1
USA type, species, or strain of bacterium
- 2
datedAn oval bacterium, as distinguished from a spherical coccus or rod-shaped bacillus
- 3
USproscribedAlternative form of bacterium
- 4
derogatoryslangLowlife, slob (could be treated as plural or singular)
bacterium
- 1
A single-celled organism with cell walls but no nucleus or organelles
Source: the English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0); obsolete, archaic, dialect and rare senses left out.
Which is more common, bacteria or bacterium?
bacteria appears 15 times per million words; bacterium 1.1 times per million words.
bacteria 15 times per million wordsbacterium 1.1 times per million words
Source: written frequency: wordfreq 3.1 (a 2021 snapshot of Wikipedia, subtitles, news, books, web text and social media).
How many people search bacteria vs bacterium?
“bacteria vs bacterium” is searched about 1,600 times a month on Google and 40 on Bing in the United States. Google counts close variants of a query together (“bacterium vs bacteria”, “bacteria or bacterium”).
Sources: Google Ads keyword data through DataForSEO and Microsoft Advertising keyword data through DataForSEO, the average month from September 2025 to August 2026.