critical mass

American  

[krit-i-kuhl mas] / ˈkrɪt ɪ kəl ˈmæs /

noun

1. Physics. the amount of a given fissionable material necessary to sustain a chain reaction at a constant rate.

   The critical mass for a bomb based on uranium fission is different than that for plutonium fission.

2. an amount necessary or sufficient to have a significant effect or to achieve a result.

   a critical mass of popular support.

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critical mass British  

noun

1. the minimum mass of fissionable material that can sustain a nuclear chain reaction

2. the minimum amount of money or number of people required to start or sustain an operation, business, process, etc

   the critical mass for a subscription digital sports channel

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Etymology

Origin of critical mass

First recorded in 1940–45

Example Sentences

See Examples For:

critical mass

“I have a good level of confidence in my conversations that we’ll have a critical mass of the right players to move this league forward.”

From The Wall Street Journal ● Sep. 8, 2026

The model of Manchester's city centre development has succeeded in creating a critical mass of population, housing, jobs and service sector activity that has allowed it to turn its significant undergraduate population into a goldmine.

From BBC ● Jul. 17, 2026

In the 2010s, conversations about women, chronic illness, and the pain gap reached critical mass.

From Salon ● Jun. 14, 2026

“For the first time in years, there is a critical mass of citizens who are done pretending that what they see before their eyes isn’t really there,” Daum wrote on her Substack.

From Los Angeles Times ● Jun. 11, 2026

Exactly how much uranium was needed to form a critical mass?

From "Bomb" by Steve Sheinkin