long-day

adjective

ˈlȯŋ-ˈdā

: responding to or relating to a long photoperiod

—used especially of a plant compare day-neutral, short-day

Word History

First Known Use

1920, in the meaning defined above

Time Traveler

The first known use of long-day was in 1920

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Cite this Entry

Style

“Long-day.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/long-day. Accessed 4 Nov. 2025.

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