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

 

photon

 noun
noun
BrE BrE//ˈfəʊtɒn//
 
; NAmE NAmE//ˈfoʊtɑːn//
 
(physics) Energy and physical forces
 
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a unit of electromagnetic energy See related entries: Energy and physical forces Word Origin early 20th cent.: from Greek phōs, phōt- ‘light’, on the pattern of electron.
See the Oxford Advanced American Dictionary entry: photon