1. : light
photeolic
photon
photography
photoperiod
2. : photograph : photographic
photofinish
photoalbum
photofilm
3. : photoelectric
photocell
photocurrent
4. : photon
photomeson
5. : photochemical
photochlorination
photoproduct
* * *
var. of photo- before a vowel: photalgia.
* * *
(or photo-) combining form
1 : related to light
photon
photography
2 : relating to photography
photocopy
photojournalism
Useful english dictionary. 2012.