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
Researchers speculate red light might benefit sleep by increasing melatonin, a hormone that helps regulate your sleep-wake cycle.5
In the morning: Red light therapy in the morning may improve mental performance.
—
Sherri Gordon, Health, 3 June 2025
White and blue light can reduce the production of melatonin, which is the hormone that regulates your sleep.
—Bestreviews, Chicago Tribune, 28 May 2025
Here’s how pineapple may help with sleep based on current research:
Melatonin content: Pineapple is one of the fruits known to contain melatonin, a hormone that regulates the sleep-wake cycle.
—Sarah Jividen, Verywell Health, 9 May 2025
Pineal calcification and melatonin dysregulation have been independently correlated with neurodegenerative diseases.
—Alyssa Goldberg, USA TODAY, 19 Mar. 2025
See All Example Sentences for melatonin
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Sherri Gordon, Health, 3 June 2025
White and blue light can reduce the production of melatonin, which is the hormone that regulates your sleep.
—Bestreviews, Chicago Tribune, 28 May 2025
Here’s how pineapple may help with sleep based on current research:
Melatonin content: Pineapple is one of the fruits known to contain melatonin, a hormone that regulates the sleep-wake cycle.
—Sarah Jividen, Verywell Health, 9 May 2025
Pineal calcification and melatonin dysregulation have been independently correlated with neurodegenerative diseases.
—Alyssa Goldberg, USA TODAY, 19 Mar. 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 13 Jun. 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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