elementary particle n
1) any of the particles of which matter and energy are composed or which mediate the fundamental forces of nature esp one (as the photon or the electron) whose existence has not been attributed to the combination of other more fundamental entities
2) one of the structural units of mitochondrial cristae that are observable by the electron microscope usu. as spheres or stalked spheres and are prob. the seat of fundamental energy-producing reactions
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any of the subatomic particles, including electrons, protons, neutrons, positrons, neutrinos, muons, etc.Medical dictionary. 2011.