- 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.
- an amount necessary or sufficient to have a significant effect or to achieve a result: a critical mass of popular support.
- the minimum mass of fissionable material that can sustain a nuclear chain reaction
- the minimum amount of money or number of people required to start or sustain an operation, business, process, etc
