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
Keep the bedroom dark by using blackout shades or curtains to promote melatonin production.
—
Cristina Mutchler, Verywell Health, 20 Sep. 2025
For a better night’s sleep, Palinski-Wade recommends reaching for melatonin-rich foods such as tart cherries, pistachios and Greek yogurt before bedtime.
—Mariette Williams, USA Today, 18 Sep. 2025
Police said no children became seriously ill, but said that the melatonin posed serious health risks.
—Emma Bussey, FOXNews.com, 18 Sep. 2025
Disruptive blue wavelengths can wreak havoc on the body’s internal clock, even suppressing the production of melatonin—a hormone that helps regulate our circadian rhythm.
—Laura Kiniry, Popular Science, 17 Sep. 2025
See All Example Sentences for melatonin
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Cristina Mutchler, Verywell Health, 20 Sep. 2025
For a better night’s sleep, Palinski-Wade recommends reaching for melatonin-rich foods such as tart cherries, pistachios and Greek yogurt before bedtime.
—Mariette Williams, USA Today, 18 Sep. 2025
Police said no children became seriously ill, but said that the melatonin posed serious health risks.
—Emma Bussey, FOXNews.com, 18 Sep. 2025
Disruptive blue wavelengths can wreak havoc on the body’s internal clock, even suppressing the production of melatonin—a hormone that helps regulate our circadian rhythm.
—Laura Kiniry, Popular Science, 17 Sep. 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 22 Sep. 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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