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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Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
Like most psychedelics, psilocybin’s effects are the result of interactions with a specific type of serotonin receptor in the brain, which both triggers the characteristic hallucinations and euphoria and induces neural plasticity. — Mike McRae 19, New Atlas, 19 Aug. 2026 Rein explains that positive interactions release a powerful mix of oxytocin, serotonin, and dopamine, akin to MDMA's effects, while isolation elevates stress hormones like cortisol. — Kevin Kruse, Forbes.com, 18 Aug. 2026 Tryptophan is an amino acid that your body uses to produce serotonin and melatonin, both of which promote relaxation and better sleep. — Mura Dominko, Martha Stewart, 9 Aug. 2026 Estrogen plays a major role in regulating the brain’s serotonin system. — Helen Carefoot, Flow Space, 5 Aug. 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 24 Aug. 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

Nglish: Translation of serotonin for Spanish Speakers

Britannica.com: Encyclopedia article about serotonin

Last Updated: - Updated example sentences
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