serotonin

noun

se·​ro·​to·​nin ˌsir-ə-ˈtō-nən How to pronounce serotonin (audio)
ˌser-
: a phenolic amine neurotransmitter C10H12N2O that is a powerful vasoconstrictor and is found especially in the brain, blood serum, and gastric mucous membrane of mammals

Examples of serotonin in a Sentence

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Ohio State Health & Discovery notes that one ounce of pistachios contains about 25 percent of your daily value of vitamin B6, which the body needs to produce serotonin and melatonin. — Samantha Agate, Charlotte Observer, 25 Oct. 2026 According to Ohio State Health & Discovery, one ounce of pistachios delivers about 25% of your daily value of vitamin B6, which the body uses to produce serotonin and melatonin. — Samantha Agate, Kansas City Star, 25 Oct. 2026 Seasonal changes are also associated with shifts in the body’s melatonin and serotonin systems. — Hanna Wickes, Miami Herald, 23 Oct. 2026 Notably, most things known to have antidepressant effects increase brain plasticity—such as exercise, electroconvulsive therapy, selective serotonin-reuptake inhibitors prescribed as antidepressants, and psychedelic drugs. — Maia Szalavitz, Scientific American, 20 Oct. 2026 See All Example Sentences for serotonin

Word History

Etymology

sero- + ton(ic) entry 2 or tone entry 1 + -in entry 1, probably after angiotonin, earlier name for angiotensin — more at angiotensin

Note: Term introduced by Maurice M. Rapport, Arda Alden Green and Irvine H. Page in "Crystalline serotonin," Science, vol. 108, Issue 2804 (September 24, 1948), pp. 329-330: "The general behavior of the crystalline substance is suggestive of its homogeneity. We would like provisionally to name it serotonin, which indicates that its source is serum and its activity is one of causing constriction."

First Known Use

1948, in the meaning defined above

Time Traveler
The first known use of serotonin was in 1948

Phrases Containing serotonin

Rhymes for serotonin

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Browse Nearby Words

serotonergic
serotonin
serotype
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Cite this Entry

“Serotonin.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/serotonin. Accessed 1 Nov. 2026.

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Medical Definition

serotonin

noun
se·​ro·​to·​nin ˌsir-ə-ˈtō-nən How to pronounce serotonin (audio) ˌser- How to pronounce serotonin (audio)
: a phenolic amine neurotransmitter C10H12N2O that is a powerful vasoconstrictor and is found especially in the brain, blood serum, and gastric mucous membrane of mammals

called also 5-HT, 5-hydroxytryptamine

More from Merriam-Webster on serotonin

Britannica.com: Encyclopedia article about serotonin

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