bacteria

Word family

• bacterium
  nounC1
• bacterial
  adjectiveB2
• antibacterial
  adjectiveB2
• bacteriology
  nounC2
• bacteriologist
  nounC2

Synonym discussion

Sense: noun/1

All four words refer to tiny living things, but they are not interchangeable. Bacteria is a precise scientific term for single-celled organisms; you can talk about both helpful and harmful bacteria. Germs is the everyday, informal word and almost always carries a negative meaning — parents tell children to wash off germs before dinner, not bacteria. Microbes is a wider umbrella term that covers bacteria along with fungi, viruses, and other microscopic life, so a science article about soil might prefer microbes. Viruses are biologically different — they are much smaller than bacteria and need a host cell to reproduce, so flu and COVID-19 are caused by viruses, while strep throat is caused by bacteria. In short: use germs in casual talk, bacteria in school or medical contexts, microbes when grouping different microscopic life forms, and viruses only for that specific group.

Common collocations

Etymology

Borrowed into English in the mid-1800s as scientists began studying tiny organisms under stronger microscopes. It is the plural of the Modern Latin word bacterium, which scientists built from the Greek baktērion, meaning a small staff or rod, because the first bacteria seen under the lens looked like little rods. The English plural bacteria became far more common in everyday use than the singular, and today many speakers treat it as if it were a mass noun like rice or water.