Word.ws English Dictionary

melatonin

/ˌmɛləˈtəʊnɪn/US/ˌmɛləˈtoʊnɪn/

melatonin noun: a 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.

Noun

melatonin (usually uncountable, plural melatonins)

  1. (usually) A 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.
    • 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
  2. (usually) Any material similar in its chemistry and effect to the natural hormone.

melatonin meaning in Tamil, Odia, Persian and Thai

melatonin in Tamil

hormone
மெலட்டோனின் melaṭṭōṉiṉ

melatonin in Odia

hormone
ମେଲାଟୋନିନ melāṭonina

melatonin in Persian

hormone
ملاتونین

melatonin in Thai

hormone
เมลาโทนิน

Forms of melatonin

pluralmelatonins

Origin of melatonin

From mela- + tone + -in, ultimately from Ancient Greek μέλας (mélas, “black, dark”).

Words formed from melatonin

Questions about melatonin

What does melatonin mean?
Melatonin means a 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.
What is melatonin in Tamil?
Melatonin in Tamil is மெலட்டோனின் (melaṭṭōṉiṉ). See Melatonin meaning in Tamil.
What part of speech is melatonin?
Melatonin is a noun.
How do you pronounce melatonin?
Melatonin is pronounced /ˌmɛləˈtəʊnɪn/ (UK).
What is the plural of melatonin?
The plural of melatonin is melatonins.

Words near melatonin in the dictionary

  1. melastomes
  2. melasus
  3. melasyenite
  4. melatonergic
  5. melatonergics
  6. melatonin
  7. melatoninergic
  8. melatonins
  9. melatope
  10. melatopes
  11. melatroctolite

Source and license

Adapted from Wiktionary: melatonin (page history and authors). Text available under the Creative Commons Attribution-ShareAlike 4.0 license. Word.ws reformatted the entry and added links. Wiktionary data of 2026-09-02.

Last updated:

Pronunciation audio from Wikimedia Commons, each file under its own free license: LL-Q1860 (eng)-Tesco250-melatonin.wav.

Cite this entry: “melatonin.” Word.ws, https://word.ws/melatonin. Based on Wiktionary, CC BY-SA 4.0.