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[foh-tuh-peer-ee-uh d] /ˌfoʊ təˈpɪər i əd/
noun, Biology
the interval in a 24-hour period during which a plant or animal is exposed to light.
Origin of photoperiod
1915-20; photo- + period
Related forms
[foh-tuh-peer-ee-od-ik] /ˌfoʊ təˌpɪər iˈɒd ɪk/ (Show IPA),
photoperiodical, adjective
photoperiodically, adverb Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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Examples from the web for photoperiod
  • Response to day-length, or photoperiod, is a gene-based trait that affects the mosquitoes seasonal life cycle.
  • The photoperiod plays an important role as noted above.
British Dictionary definitions for photoperiod


the period of daylight in every 24 hours, esp in relation to its effects on plants and animals See also photoperiodism
Derived Forms
photoperiodic, adjective
photoperiodically, adverb
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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photoperiod in Medicine

photoperiod pho·to·pe·ri·od (fō'tō-pĭr'ē-əd)
The duration of an organism's daily exposure to light, considered especially with regard to the effect of such exposure on growth and development.

pho'to·pe'ri·od'ic (-ŏd'ĭk) or pho'to·pe'ri·od'i·cal (-ĭ-kəl) adj.
The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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photoperiod in Science
The duration of an organism's daily exposure to light, considered especially with regard to the phenomena of photoperiodism.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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