Definition of proton noun from the Oxford Advanced Learner's Dictionary

 

proton

 noun
noun
BrE BrE//ˈprəʊtɒn//
 
; NAmE NAmE//ˈproʊtɑːn//
 
(physics) Molecules and matter
 
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a very small piece of matter (= a substance) with a positive electric charge that forms part of the nucleus (= central part) of an atom see also electron, neutron Wordfinderantiparticle, atom, electron, ion, neutron, nucleus, particle, positron, proton, valency See related entries: Molecules and matter Word Origin 1920s: from Greek, neuter of prōtos ‘first’.
See the Oxford Advanced American Dictionary entry: proton