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photomicrograph
photomontage
photomosaic
photomultiplier
photon
photonegative
photonics
photonuclear
photoperiod
photoperiodism
photopheresis
photophilic
photophobia
photophobic
photophore
photophoresis
photophosphorylation
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photoperiod
pho·to·pe·ri·od [ ftō pree əd ] (plural pho·to·pe·ri·ods)


noun 
Definition:
 
daily cycle of light and darkness: the daily cycle of light and darkness that affects the behavior and physiological functions of organisms

pho·to·pe·ri·od·ic [ ftō peeree óddik ] adjective
pho·to·pe·ri·od·i·cal·ly [ ftō pree óddikəlee ] adverb
Encarta® World English Dictionary [North American Edition] © & (P)2009 Microsoft Corporation. All rights reserved. Developed for Microsoft by Bloomsbury Publishing Plc.
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