melatonin
noun
mel·a·to·nin
ˌme-lə-ˈtō-nən 
: a vertebrate hormone that is derived from serotonin, is secreted by the pineal gland especially in response to darkness, and has been linked to the regulation of circadian rhythms
Examples of melatonin in a Sentence
Recent Examples on the Web
Tart Cherry Tart cherries can also be a natural alternative to melatonin.
—
Ayesha Gulzar, Verywell Health, 21 July 2025
Not just the usual suspects — vitamins and minerals — but also items as varied as turmeric, fish oil, probiotics and melatonin — as well as combinations that purport to burn fat (not muscle!), cure erectile dysfunction and boost memory.
—Andrea Kane, CNN Money, 15 July 2025
Human health, how exposure to light at night affects chemical reactions during our sleeping patterns, our circadian rhythm and effectively affecting melatonin cycles.
—Anthony Wood, Space.com, 2 July 2025
And this one appears to enhance melatonin synthesis via SAM methylation—a novel pathway.
—Lucy Notarantonio, MSNBC Newsweek, 21 June 2025
See All Example Sentences for melatonin
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Ayesha Gulzar, Verywell Health, 21 July 2025
Not just the usual suspects — vitamins and minerals — but also items as varied as turmeric, fish oil, probiotics and melatonin — as well as combinations that purport to burn fat (not muscle!), cure erectile dysfunction and boost memory.
—Andrea Kane, CNN Money, 15 July 2025
Human health, how exposure to light at night affects chemical reactions during our sleeping patterns, our circadian rhythm and effectively affecting melatonin cycles.
—Anthony Wood, Space.com, 2 July 2025
And this one appears to enhance melatonin synthesis via SAM methylation—a novel pathway.
—Lucy Notarantonio, MSNBC Newsweek, 21 June 2025
See All Example Sentences for melatonin
Cite this Entry
“Melatonin.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/melatonin. Accessed 29 Jul. 2025.
Copy CitationKids Definition
melatonin
noun
mel·a·to·nin
ˌmel-ə-ˈtō-nən
: a hormone that is secreted by the pineal gland especially in response to darkness and has been linked to the regulation of bodily functions or activities (as sleep) that occur in approximately 24 hour cycles
Medical Definition
melatonin
noun
mel·a·to·nin
ˌmel-ə-ˈtō-nən
: a vertebrate hormone C13H16N2O2 that is derived from serotonin, is secreted by the pineal gland especially in response to darkness, and has been linked to the regulation of circadian rhythms
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