- a quantum of electromagnetic radiation, regarded as a particle with zero rest mass and charge, unit spin, and energy equal to the product of the frequency of the radiation and the Planck constant
WordReference Random House Learner's Dictionary of American English © 2026
pho•ton /ˈfoʊtɑn/USA pronunciation
n. [countable]
WordReference Random House Unabridged Dictionary of American English © 2026- Physicsa unit of measure of electromagnetic radiation.
pho•ton
(fō′ton),USA pronunciation n.
- Physicsa quantum of electromagnetic radiation, usually considered as an elementary particle that is its own antiparticle and that has zero rest mass and charge and a spin of one. Symbol: γ Also called light quantum.
- phot- + -on1 1900–05
Collins Concise English Dictionary © HarperCollins Publishers::
photon /ˈfəʊtɒn/ n
'photon' also found in these entries (note: many are not synonyms or translations):
boson
- chronon
- corpuscular theory
- electromagnetic radiation
- Geiger counter
- graviton
- mole
- -on
- photoelectron
- recoil
- elementary particle
- gamma ray
- light quantum
- massless
- on
- pair production
- phonon
- photodisintegration
- photofission
- photonic
- proportional counter
- reaction
- resonance radiation
- Ritz combination principle
- scintillate
- scintillation
- SPECT