serotonin

American  

[ser-uh-toh-nin, seer-] / ˌsɛr əˈtoʊ nɪn, ˌsɪər- /

noun

Biochemistry.

• serotonins
  plural

1. a neurotransmitter, derived from tryptophan, that is involved in sleep, depression, memory, and other neurological processes.

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serotonin British  

/ ˌsɛrəˈtəʊnɪn /

noun

1. a compound that occurs in the brain, intestines, and blood platelets and acts as a neurotransmitter, as well as inducing vasoconstriction and contraction of smooth muscle; 5-hydroxytryptamine (5HT)

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serotonin Scientific  

/ sĕr′ə-tō′nĭn,sîr′- /

1. A monoamine substance that is formed from tryptophan and found in many animal tissues, including the intestine and central nervous system. In the brain, serotonin acts as a neurotransmitter that is involved in the control of pain perception, the sleep-wake cycle, and mood. Serotonin is also produced in some bacteria and plants.

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Other Word Forms

Noun Inflected Forms

• serotonins
  plural

Etymology

Origin of serotonin

First recorded in 1945–50; sero- + tone + -in ²

Compare meaning

How does serotonin compare to similar and commonly confused words? Explore the most common comparisons:

• dopamine vs. serotonin

Explanation

Serotonin is a chemical in the human body known as the “feel-good chemical.” It helps regulate things like mood, sleep, and appetite. Some of it is in your brain but most of it is in your gut. Serotonin helps cells talk to each other. As serotonin has been studied by scientists over the years, it's become clear how important it is for helping people avoid depression and anxiety. With enough serotonin in your brain, you're able to sleep soundly, learn new things, and remember things clearly. Serotonin also helps with digestion, blood clotting, and bone density. Doctors first discovered serotonin in the 1940s.

Example Sentences

See Examples For:

serotonin serotonins

Selective serotonin reuptake inhibitors are a widely used class of antidepressants.

From Science Daily ● Aug. 24, 2026

But by increasing blood flow, reducing muscle stiffness and increasing serotonin, a hard massage can take on “some components of travel fatigue,” Katzenback said.

From The Wall Street Journal ● Jul. 21, 2026

The findings suggest that an already damaged valve may be especially vulnerable when serotonin exposure, reduced transporter activity, and genetic susceptibility occur together.

From Science Daily ● Jul. 12, 2026

A study published in 2025 investigated serotonin in aortic stenosis, a different type of heart valve disease.

From Science Daily ● Jul. 12, 2026

The second stage, attraction, is governed by dopamine and serotonin.

From "The Sun Is Also a Star" by Nicola Yoon

The presence of this person makes you release all kinds of substances in your brain, serotonins and endorphins.

From Los Angeles Times ● Nov. 6, 2015