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

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

Scientists need a critical mass of data to be able to identify statistically significant patterns.

From Los Angeles Times ● Jun. 15, 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

This means that when a hub reaches critical mass it can survive policy errors that would cripple a challenger.

From The Wall Street Journal ● Feb. 9, 2026

When the two pieces met, they would form a critical mass, the amount of material needed to get a chain reaction going.

From "Bomb" by Steve Sheinkin