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Dictionary

pi•on

Pronunciation: (pī'on), [key]
—n. Physics.
the first meson to be discovered: it has spin 0 and may be positively or negatively charged or neutral; charged pions decay into a muon and a neutrino or antineutrino. Symbol: π Also called pi meson.

Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.

piolet

pioneer

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