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Melatonin is a chemical the brain makes, mostly at night, that helps the body know it is time to sleep. Darkness tells the body to make more; bright light tells it to make less. That is its first job — it is a hormone, a message chemical inside you. People also buy melatonin as a pill or drop to help with sleep or with jet lag after a long flight. In a shop it can look like just another sleep sweet, but it is still that same body chemical, not a magic knock-out drug, and more is not always kinder to you.
褪黑激素（台灣常當助眠保健品來買）
組成From mela- + tone + -in, ultimately from Ancient Greek μέλας (mélas, black, dark). The mela- piece points to darkness.
同家族的字
- melaninthe mela- piece is from Greek μέλας, dark, the same root as in melanin
原始詞典資料2 筆記錄
以下是外部詞典記錄的用法，原文照列，我們還沒有寫成教學內容。上面的說明才是我們自己寫的；有些用法可能上面已經講過了。
melatoninnoun/ˌmɛləˈtəʊnɪn/
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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.
- Melatonin production can be delayed or arrested by even brief flashes of bright light entering the eye, research has shown.
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Any material similar in its chemistry and effect to the natural hormone.
資料來源：英文維基詞典 English Wiktionary（CC BY-SA 4.0）。 原文照列，未經改寫。