noun Etymology: Greek melas black + -tonin (as in serotonin) Date: 1958 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
MELATONIN
Meaning of MELATONIN in English
Merriam Webster. Explanatory English dictionary Merriam Webster. Толковый словарь английского языка Мерриам-Уэбстер. 2012