serotonin

noun

se·​ro·​to·​nin ˌsir-ə-ˈtō-nən 

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

Recent Examples on the Web

The soil bacterium Mycobacterium vaccae, which children encounter through outdoor play and in a garden, activates the same serotonin neurons that antidepressants target. —John La Puma, Oc Register, 26 Mar. 2026

Tryptophan, for example, is an essential amino acid the body converts into serotonin and melatonin — hormones that help control sleep timing. —Peter Burke, FOXNews.com, 18 Mar. 2026

Other medication classes, such as serotonin-norepinephrine reuptake inhibitors (SNRIs), atypical antidepressants or tricyclic antidepressants, may also be used depending on individual needs. —Daryl Austin, USA Today, 14 Mar. 2026

The untitled track comes with a serotonin-providing video of a person—perhaps the Norwegian singer/composer herself—skipping down a road carrying a baby, with a brief cameo from a similarly cheerful dog. —Jazz Monroe, Pitchfork, 13 Mar. 2026

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

Phrases Containing serotonin

• selective serotonin reuptake inhibitor

Rhymes for serotonin

• calcitonin
• digitonin
• melatonin
• kronen
• onan
• phonon
• ronin
• santonin

Medical Definition

serotonin

noun

se·​ro·​to·​nin ˌsir-ə-ˈtō-nən  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

called also 5-HT, 5-hydroxytryptamine