photoperiod

noun

pho·​to·​pe·​ri·​od ˌfō-tō-ˈpir-ē-əd How to pronounce photoperiod (audio)
: a recurring cycle of light and dark periods of constant length
also : photophase sense 2
photoperiodic
ˌfō-tō-ˌpir-ē-ˈä-dik How to pronounce photoperiod (audio)
adjective
photoperiodically
ˌfō-tō-ˌpir-ē-ˈä-di-k(ə-)lē How to pronounce photoperiod (audio)
adverb

Examples of photoperiod in a Sentence

Recent Examples on the Web
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
This study opens the door to further insights into just how day length (photoperiod) and sun intensity can impact energy levels and help those with more severe 'winter blues' proactively improve seasonal mental wellbeing. — Bronwyn Thompson september 29, New Atlas, 29 Sep. 2024 For example, long-distance migratory songbirds set their internal clocks to the photoperiod and use the summer solstice to time their nesting and migration, said Saeedeh Bani Assadi, a biologist at the University of Manitoba. — Quanta Magazine, 18 June 2024

Word History

First Known Use

1920, in the meaning defined above

Time Traveler
The first known use of photoperiod was in 1920

Rhymes for photoperiod

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photoperiod
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Cite this Entry

“Photoperiod.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/photoperiod. Accessed 10 Mar. 2025.

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Kids Definition

photoperiod

noun
pho·​to·​pe·​ri·​od ˌfōt-ō-ˈpir-ē-əd How to pronounce photoperiod (audio)
: a recurring cycle of light and dark periods as it affects the growth and functioning of a plant or animal

Medical Definition

photoperiod

noun
pho·​to·​pe·​ri·​od ˌfōt-ō-ˈpir-ē-əd How to pronounce photoperiod (audio)
: a recurring cycle of light and dark periods of constant length
photoperiodic
-ˌpir-ē-ˈäd-ik How to pronounce photoperiod (audio)
adjective
photoperiodically
-i-k(ə-)lē How to pronounce photoperiod (audio)
adverb
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