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photo-

a combining form meaning “light” (photobiology); also used to represent “photographic” or “photograph” in the formation of compound words: photocopy.

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Also especially before a vowel, phot-.

Origin of photo-

< Greek, combining form of phôs (genitive phōtós)
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
British Dictionary definitions for photo-

photo-

combining form

of, relating to, or produced by lightphotosynthesis
indicating a photographic processphotolithography

Word Origin for photo-

from Greek phōs, phōt- light
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
Word Origin and History for photo-

word-forming element meaning "light" or "photographic" or "photoelectric," from Greek photo-, comb. form of phos (genitive photos) "light," from PIE root *bha- "to shine" (see phantasm).

Online Etymology Dictionary, © 2010 Douglas Harper
Medicine definitions for photo-

photo-

pref.

Light; radiant energy:photosynthesis.
Photographic:photofluorography.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
Science definitions for photo-

photo-

A prefix that means “light,” as in photoreceptor.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.