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critical mass

Physics. the amount of a given fissionable material necessary to sustain a chain reaction at a constant rate.
an amount necessary or sufficient to have a significant effect or to achieve a result:
a critical mass of popular support.
Origin of critical mass
1940-45 Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2016.
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British Dictionary definitions for critical-mass

critical mass

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: the critical mass for a subscription digital sports channel
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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critical-mass in Science
critical mass  
  1. The smallest mass of a fissionable material that will sustain a nuclear chain reaction.

  2. The amount of matter needed to generate sufficient gravitational force to halt the current expansion of the universe. See also big bang, big crunch.

The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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critical-mass in Culture

critical mass definition

In physics, the amount of material that must be present before a chain reaction can sustain itself.

Note: The term critical mass is used to refer generally to the minimum amount of something needed to produce a given effect: “The town needs a critical mass of industry to attract more business.”
The American Heritage® New Dictionary of Cultural Literacy, Third Edition
Copyright © 2005 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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