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English definition of “melatonin”

melatonin

noun [U]     /mel.əˈtəʊ.nɪn/ US  /-ˈtoʊ-/ specialized
a hormone in the body that produces changes in skin colour and is involved in continuing biorhythms such as our sleep patternSubstances and structures in the body
(Definition of melatonin noun from the Cambridge Advanced Learner's Dictionary & Thesaurus © Cambridge University Press)
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