Definition of "pion"
noun:
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Any of three semistable mesons, having positive, negative or neutral charge, composed of up and down quarks/antiquarks.
from Wiktionary, Creative Commons Attribution/Share-Alike License
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Any of three semistable mesons, having positive, negative or neutral charge, composed of up and down quarks/antiquarks.
from Wiktionary, Creative Commons Attribution/Share-Alike License