melatonin

/ˈmɛləˌtoʊnən/

/mɛləˈtʌʊnɪn/

Melatonin is a hormone your body produces to help regulate your sleep cycle. Sometimes people take a melatonin supplement at night to help them get a better night's rest.

You might think of melatonin as a nighttime hormone, and you'd be right — darkness actually stimulates the release of melatonin. Its name reflects this fact: the Greek root is melas, "black or dark." Scientists suspect that our modern lifestyle (electric lights, computer screens, and night shifts at work) can have harmful effects on the body's ability to produce and regulate melatonin, which not only makes us sleepy, but may protect against neurological conditions like Alzheimer's disease.

Definitions of melatonin

1. noun

   sleep-regulating hormone secreted by the pineal gland
   type of:

   endocrine, hormone, internal secretion

   the secretion of an endocrine gland that is transmitted by the blood to the tissue on which it has a specific effect