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

In a fragmented media world where critical mass is becoming harder to attain, Navarro has become one of media’s most recognizable political talking heads thanks to her two high-profile TV roles.

From Los Angeles Times • May 10, 2026

The situation came to a critical mass in 2024 when Musk sued OpenAI for diverging from its nonprofit mission.

From Slate • Apr. 30, 2026

Participants at the Santa Marta meeting believe the real purpose of the meeting is to show those who are hesitating about the transition that there is a critical mass moving in favour of renewables.

From BBC • Apr. 24, 2026

"It'll hit a critical mass at some point, and maybe become as commonplace as smartwatches or glasses," he said.

From Barron's • Jan. 8, 2026

The critical mass of plutonium would not stay together long enough to create a massive atomic explosion.

From "Bomb" by Steve Sheinkin