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

Wood Mackenzie reckons the metals-intensive energy transition has, in the meantime, reached critical mass and will continue independently of political influences.

From The Wall Street Journal • Jan. 20, 2026

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

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

“What is less obvious is whether that will create the critical mass necessary to overcome the obstacles standing in the way of sports betting in the states that have yet to authorize it.”

From Barron's • Nov. 12, 2025

But it would end up being one of many little things—a slow accrual, compounding steadily and imperceptibly toward critical mass.

From "Into Thin Air" by Jon Krakauer