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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That’s because it’s been shown to lower cortisol, boost serotonin and dopamine, encourage mindfulness, and reduce rumination, according to the report. — Michele Laufik, Martha Stewart, 3 Sep. 2026 Sugar Activates Your Brain’s Reward System Sugar triggers the brain’s reward system, boosting serotonin and dopamine levels, which are hormones that enhance mood and satisfaction. — Mira Miller, Verywell Health, 2 Sep. 2026 Serotonin-norepinephrine reuptake inhibitors or SNRIs such as Cymbalta, Fetzima and Effexor XR prevent the reabsorption of serotonin and norepinephrine, which help shape the body’s fight-or-flight response. — Jen Christensen, CNN Money, 29 Aug. 2026 Every time my phone vibrates with a new text from him and my screen lights up with his name, a shot of serotonin goes straight to my heart. — Literary Hub, 21 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 7 Sep. 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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