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

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

What happens next depends on whether this thing achieves a critical mass of meme status.

From Barron's • Apr. 16, 2026

Media fragmentation and the constant flow of information are presented as making it harder for scandals to reach critical mass, as new controversies quickly displace previous ones.

From Los Angeles Times • Nov. 30, 2025

And male monopolies on power tend to be self-perpetuating: Only when a critical mass of women run and win does it begin to feel possible that women can run for office and win.

From Slate • Nov. 22, 2025

As more join in, they seem to reach a critical mass, a quorum, and the thinking begins.

From "The Lives of a Cell" by Lewis Thomas