serotonin

American  

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

noun

Biochemistry.

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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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

Earlier studies have shown that bacteria living in the gut, known collectively as the gut microbiota, can influence how much serotonin the body produces.

From Science Daily • Mar. 13, 2026

Many mood disorders and neurodegenerative conditions, including Alzheimer's disease, are linked to disruptions in serotonin, a neurotransmitter that plays a key role in regulating mood and other brain functions.

From Science Daily • Mar. 8, 2026

Scientists have identified at least 14 different receptors that respond to the neurotransmitter serotonin.

From Science Daily • Feb. 15, 2026

Actually winning releases serotonin, a neurotransmitter associated with stabilized mood and feelings of calmness.

From The Wall Street Journal • Feb. 12, 2026

The second chemical of the attraction phase is serotonin.

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