serotonin

Etymology

It was coined from English sero- + tonic + -in:^{[2][3][4][5][6]} sero- is the combining form of serum,^[2] the middle element is taken from the adjective tonic,^[3][7] and -in is the suffix of chemical names.^[2] Merriam-Webster explains the name by the substance's constricting effect on blood vessels.^[7] The American Heritage Dictionary and Dictionary.com take the middle part from tone instead.^[8][9]

Earliest recorded meaning

The compound 5-hydroxytryptamine, found in blood serum: 1948, in a paper by M. M. Rapport and others in Science.^[3][2][7]

Semantic evolution

The name was given for the substance's presence in blood serum and its action in constricting blood vessels.^[7][10] It is now best known as a neurotransmitter, also found in the brain, the intestines and the blood platelets,^[6][10] and the OED's definition includes its role in vasoconstriction, anaphylactic shock and the regulation of daily cycles.^[3][4] The adjective serotonergic is formed from it.^[4]

Timeline

• 1948 – the compound 5-hydroxytryptamine.^[3][2][7]

Meanings

Noun

1. A compound, 5-hydroxytryptamine, present in the brain, intestines and blood platelets, which acts as a neurotransmitter and causes vasoconstriction: Some antidepressants raise serotonin levels in the brain.^[6][10][7]

Word family

• selective serotonin reuptake inhibitor

Related words

• serotonergic
• serum
• tonic
• melatonin

References

1. ^ a b Wiktionary, the free dictionary, https://en.wiktionary.org
2. ^ a b c d e Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
3. ^ a b c d e Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
4. ^ a b c Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press
5. ^ Stevenson, Angus, ed. (2010), Oxford Dictionary of English, 3rd ed., Oxford: Oxford University Press
6. ^ a b c Collins English Dictionary (2023), Glasgow: HarperCollins
7. ^ a b c d e f Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
8. ^ The American Heritage Dictionary of the English Language (online 2024), 5th ed., Boston: Houghton Mifflin Harcourt
9. ^ Dictionary.com Unabridged (2016), based on the Random House Unabridged Dictionary, New York: Random House
10. ^ a b c Soanes, Catherine; Stevenson, Angus, eds. (2004), Concise Oxford English Dictionary, 11th ed., Oxford: Oxford University Press