Pronunciation (US) IPA (key): /bækˈtɪr.i.ə/ (UK) IPA (key): /bækˈtɪər.ɪ.ə/ Audio (US)(file) Noun Singular bacterium Plural bacteria The plural form of bacterium; more than one (kind of) bacterium. Wikiwand - on Seamless Wikipedia browsing. On steroids.Remove ads