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A physical constant often used in quantum mechanics, equal to h/2π , where h equals Planck's constant. Its symbol is ħ. Also called h-bar, reduced Planck's constant.
[After Paul Adrien Maurice Dirac.]
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.