Melatonin Meaning
/ˌmɛləˈtəʊnɪn/Definition, CEFR level B2, pronunciation, examples, and quiz.
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Definition
nounA hormone, related to serotonin, that is secreted by the pineal gland, and stimulates colour change in the skin of reptiles, and is involved in the sleep and wake and reproductive cycles in mammals.
nounAny material similar in its chemistry and effect to the natural hormone.
Sentence Examples
The pineal gland secretes melatonin.
Melatonin helps to regulate circadian rhythms.
CEFR Practice Quiz
The doctor prescribed a daily ____ supplement to help treat her insomnia.
CEFR Practice Quiz (Alternate)
Some people take ____ supplements to help regulate their sleep patterns when traveling across time zones.
Word Origin & History
From mela- + tone + -in, ultimately from Ancient Greek μέλας (mélas, “black, dark”).
Literary Quotations & Historical Citations
"How exactly melatonin relates to sleep is still not understood."
— 2019, Bill Bryson, The Body: A Guide for Occupants, Black Swan (2020), page 310:
"Melatonin production can be delayed or arrested by even brief flashes of bright light entering the eye, research has shown."
— 2025 December 9, Veronique Greenwood, “Your Bedroom Probably Isn't Dark Enough”, in TIME:
Explore More B2 Vocabulary Words
CEFR Practice Quiz
The doctor prescribed a daily ____ supplement to help treat her insomnia.
CEFR Practice Quiz (Alternate)
Some people take ____ supplements to help regulate their sleep patterns when traveling across time zones.