pho·​to·​pe·​ri·​od·​ism ˌfō-tō-ˈpir-ē-ə-ˌdi-zəm How to pronounce photoperiodism (audio)
: a plant's or animal's response or capacity to respond to photoperiod

Example Sentences

Recent Examples on the Web The process is called photoperiodism. Eric Betz, Discover Magazine, 19 Dec. 2017

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'photoperiodism.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History

First Known Use

circa 1911, in the meaning defined above

Time Traveler
The first known use of photoperiodism was circa 1911

Dictionary Entries Near photoperiodism

Cite this Entry

“Photoperiodism.” Dictionary, Merriam-Webster, Accessed 3 Jun. 2023.

Medical Definition


pho·​to·​pe·​ri·​od·​ism -ˈpir-ē-ə-ˌdiz-əm How to pronounce photoperiodism (audio)
variants also photoperiodicity
plural photoperiodisms also photoperiodities
: the response or the capacity to respond to photoperiod

More from Merriam-Webster on photoperiodism

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