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photo-

1.
a combining form meaning “light” (photobiology); also used to represent “photographic” or “photograph” in the formation of compound words:
photocopy.
Also, especially before a vowel, phot-.
Origin
< Greek, combining form of phôs (genitive phōtós)
Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
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British Dictionary definitions for photo-

photo-

combining form
1.
of, relating to, or produced by light photosynthesis
2.
indicating a photographic process photolithography
Word Origin
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
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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
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photo- in Medicine

photo- or phot-
pref.

  1. Light; radiant energy: photosynthesis.

  2. Photographic: photofluorography.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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photo- in Science
photo-  
A prefix that means "light," as in photoreceptor.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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Difficulty index for photo-

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Word Value for photo

10
10
Scrabble Words With Friends

Quotes with photo-