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

At one point Karp tried to rally the troops and attempted to organize a joint letter, but a critical mass wouldn’t sign on.

From The Wall Street Journal • Feb. 6, 2026

With such fragmentation, it’s much harder for a negative storyline to reach critical mass.

From Los Angeles Times • Nov. 30, 2025

“But they’ll never achieve the same critical mass of awfulness ever again. Even at MTSU.”

From "The Serpent King" by Jeff Zentner