germ theory

American  

noun

1. Pathology. the theory that infectious diseases are due to the agency of germs or microorganisms.

2. Biology. biogenesis.

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germ theory British  

noun

1. the theory that all infectious diseases are caused by microorganisms

2. the theory that living organisms develop from other living organisms by the growth and differentiation of germ cells

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Etymology

Origin of germ theory

First recorded in 1870–75

Example Sentences

The author appreciates what a terrific advance modern germ theory represents, but she also recognizes its tendency to generate absurd excesses.

From The Wall Street Journal • Jan. 23, 2026

For a man who claims it's time for a "break" in medical research into infectious disease, it was likely an irritating irony to present such a compelling reminder of the validity of germ theory.

From Salon • Jan. 30, 2025

The process of heating milk to a specific temperature for a specific period of time and then allowing it to rapidly chill is named for the French chemist and germ theory pioneer Louis Pasteur.

From Los Angeles Times • May 12, 2024

In the nineteenth century, Louis Pasteur’s germ theory also further shored up medical support for shaving: Facial hair, doctors warned, was a microbe haven.

From National Geographic • Nov. 7, 2023

Pasteur's "germ theory" will lead to a revolution in medicine.

From "Phineas Gage" by John Fleischman