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A principle in physics stating that two systems that are mirror images of each other, such as left-spinning and right-spinning particles, should behave identically. The principle does not hold for weak interactions of subatomic particles.
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.