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

Magnesium may help melatonin work better.5 Magnesium for athletic performance: The evidence conflicts, but some people take it before a workout to reduce sore muscles.6 Calcium carbonate: Take this supplement with food. —Amber J. Tresca, Verywell Health, 19 Feb. 2025

The new study highlights that drinking coffee in the afternoon can disrupt circadian rhythms, which reduces melatonin production. —Stephanie Brown, Verywell Health, 18 Jan. 2025

Authorities have accused the women of giving excessive amounts of medication to children at the day care, dosing them with Benadryl and melatonin before their naps. —Michael Gfoeller and David H. Rundell, Newsweek, 16 Jan. 2025

They’re packed with tyramine and histamines, which interfere with melatonin production—your body’s natural sleep hormone. —Bryan Robinson, Forbes, 7 Dec. 2024

Word History

Etymology

mela-, extracted from Greek melan-, mélās "black, dark" + -tonin (in serotonin); so named because the hormone can lighten skin color in animals by reversing the effect of melanocyte-stimulating hormones — more at melano-

Note: The word was probably introduced in the first published description of the hormone's isolation: Aaron B. Lerner, et al., "Isolation of melatonin, the pineal gland factor that lightens melanocytes," Journal of the American Chemical Society, vol. 80, no. 10 (May 20, 1958), p. 2587.

First Known Use

1958, in the meaning defined above

Rhymes for melatonin

• calcitonin
• digitonin
• serotonin
• kronen
• onan
• phonon
• ronin
• santonin

Kids 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