1.  critical mass(n = noun.attribute) - the minimum amount (of something) required to start or maintain a venture; "the battle for the computer market has now reached critical mass"; "there is now a critical mass of successful women to take the lead"; "they sold the business because it lacked critical mass"
is a kind of amount

2.  critical mass(n = noun.attribute) - the minimum mass of fissionable material that can sustain a chain reaction;
is a kind of mass

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