Meaning of PHOTO- in English
a combining form meaning "light" ( photobiology ); also used to represent "photographic" or "photograph" in the formation of compound words: photocopy.
Also, esp. before a vowel, phot- .
[ phôs (gen. photós ) ]
Random House Webster's Unabridged English dictionary. Полный английский словарь Вебстер - Random House . 2012