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subatomic particle

n.

Any of various units of matter below the size of an atom, including the elementary particles and hadrons.

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The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

Science definitions for subatomic particle

subatomic particle

[sŭb′ə-tŏm′ĭk]

Any of various particles of matter that are smaller than a hydrogen atom. Protons, neutrons, and electrons are subatomic particles, as are all hadrons and leptons. See also composite particle elementary particle.

The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.