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

"We've suspected that serotonin was involved in tinnitus, but we didn't really understand how," said co-author Zheng-Quan Tang, Ph.D., of Anhui University in China.

From Science Daily • May 15, 2026

Amir Khan, a doctor, broadcaster and president of the RSPB, said: "Hearing birdsong, especially during the dawn chorus when they're at their loudest and most beautiful, can produce more serotonin and make us feel good."

From BBC • May 9, 2026

Many have been helped by antidepressants, the most common of which are so-called selective serotonin reuptake inhibitors, or SSRIs, sold under the brand names Zoloft and Lexapro.

From The Wall Street Journal • May 4, 2026

When acetylcholine was introduced to lab-grown gut tissue containing EC cells, those cells responded by releasing serotonin.

From Science Daily • Mar. 28, 2026

When couples confess that they can’t stop thinking about each other, it’s because their serotonin level has dropped.

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