Plural of bacillus

irregular plural

The plural of bacillus is bacilli.

Forms of bacillus

Fusobacteria are fusiform bacilli (spindled rods).From the entry fusiform
One lie in the presence of a policeman seemed to multiply like bacilli.1974, Graham Greene, The Honorary Consul, New York: Pocket Books, page 94. From the entry bacilli
Such media are called differential media (e.g., eosin methylene blue or MacConkey agar) and are commonly used to isolate enteric bacilli.1996, Samuel Baron, editor, Medical Microbiology. From the entry medium
Beraneck's tuberculin consists of equal parts of the filtrate of a culture of tubercle bacilli and a 1 per cent. orthophosphoric extract of the residue.1916, Alexander Bryan Johnson, General topics, blood vessels, plastic operations, muscles, nerves, wounds, radium, page 216. From the entry orthophosphoric
Stained bacilli, when examined with the polarising microscope, often show a doubly refractile cell wall (e. g., B. tuberculosis and B. anthracis).1913, John William Henry Eyre, The Elements of Bacteriological Technique. From the entry refractile

noun Any of various rod-shaped, spore-forming aerobic bacteria in the genus Bacillus, some of which cause disease.
noun Any bacilliform (rod-shaped) bacterium.
noun Something which spreads like bacterial infection.

Adapted from Wiktionary: bacillus (page history and authors) and the entries of its forms. Text available under the Creative Commons Attribution-ShareAlike 4.0 license. Word.ws left out forms marked obsolete, archaic, rare or dialectal and added the examples. Wiktionary data of 2026-09-02.

Last updated: 2026-09-02

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