pho·ton 
(fōtŏn′)
(fōtŏn′)n.
The elementary particle of light and other electromagnetic radiation; the quantum of electromagnetic energy. The photon is the massless, neutral vector boson that mediates electromagnetic interactions.
pho·tonic adj.
- irrecusably
- irredeemable
- irredeemably
- irredenta
- irredentism
- irredentist
- irreducibility
- irreducible
- irreducibleness
- irreducibly
- irrefragability
- irrefragable
- irrefragably
- irrefrangible
- irrefrangibly
- irrefutability
- irrefutable
- irrefutably
- irreg.
- irregardless
- irregular
- irregular galaxy
- irregularity
- irregularly
- irrelative