Home › Words › M › melatoninmelatonin/ˌmɛləˈtəʊnɪn/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.melatonin is pronounced /ˌmɛləˈtəʊnɪn/.EtymologyFrom mela- + tone + -in, ultimately from Ancient Greek μέλας (mélas, “black, dark”).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.e.g.“How exactly melatonin relates to sleep is still not understood.” — 2019, Bill Bryson, The Body: A Guide for Occupants, Black Swan (2020), page 310:Any material similar in its chemistry and effect to the natural hormone.Definitions & examples from Wiktionary (CC BY-SA 3.0).Words closest in meaningBy meaning, not spelling — each word's AI semantic fingerprint, nearest first.pinealocyte 58% match — A single cell within the pineal gland which is involved in melatonin secretion and circadian rhythms. vs melatonin →normelatonin 54% match — Synonym of acetylserotonin. vs melatonin →melanocortin 54% match — Any of a group of pituitary peptide hormones vs melatonin →melanocortic 54% match — Relating to melanocortins vs melatonin →acetylserotonin 53% match — The N-acetyl derivative of serotonin; it is an intermediate in the biosynthesis of melatonin from serotonin vs melatonin →promelanin 53% match — That promotes the formation of melanin vs melatonin →conarium 53% match — The pineal gland. vs melatonin →melanocyte 52% match — A cell in the skin that produces the pigment melanin. vs melatonin →