[fot, foht] 
| a unit of illumination, equal to 1 lumen per square centimeter. Abbreviation: ph |
| var. of photo- before a vowel: photalgia. |
| a combining form meaning “light” (photobiology); also used to represent “photographic” or “photograph” in the formation of compound words: photocopy. |
| phot (fōt) n. A unit of illumination equal to one lumen per square centimeter. [Greek phōs, phōt-, light; see bhā-1 in Indo-European roots.] |
photo- or phot-
pref.
Light; radiant energy: photosynthesis.
Photographic: photofluorography.
| photo-
A prefix that means "light," as in photoreceptor. |