# serum

> English word · Noun · IPA /ˈsɪəɹəm/ · frequency rank #10,609

## Definitions
1. Ellipsis of blood serum.
2. Blood serum used as a blood product, in the practice of medicine: blood serum from the tissues of immunized animals (human or nonhuman), containing antibodies and used to transfer immunity to another individual (human or nonhuman).
3. A watery liquid from animal tissue, especially one that moistens the surface of serous membranes or that is exuded by such membranes when they become inflamed, such as in edema or a blister.
4. The watery portion of certain other animal fluids, such as milk; whey.
5. A skincare product of varying consistencies with a high concentration of one or more active ingredients, for a targeted purpose, such as preventing acne, repairing sun damage, or moisturizing.

## Etymology
From Latin serum (“whey”). Cognates include French sérum, Spanish suero, Italian siere, siero, Portuguese soro. Doublet of suero.

## Easily confused with
- **sum** (https://plainspell.com/en/vs/serum-vs-sum)
- **slum** (https://plainspell.com/en/vs/serum-vs-slum)
- **serve** (https://plainspell.com/en/vs/serum-vs-serve)
- **setup** (https://plainspell.com/en/vs/serum-vs-setup)
- **sperm** (https://plainspell.com/en/vs/serum-vs-sperm)
- **syrup** (https://plainspell.com/en/vs/serum-vs-syrup)
- **shrug** (https://plainspell.com/en/vs/serum-vs-shrug)
- **shrub** (https://plainspell.com/en/vs/serum-vs-shrub)
- **strut** (https://plainspell.com/en/vs/serum-vs-strut)
- **servo** (https://plainspell.com/en/vs/serum-vs-servo)
- **sternum** (https://plainspell.com/en/vs/serum-vs-sternum)
- **ser** (https://plainspell.com/en/vs/ser-vs-serum)
- **sem** (https://plainspell.com/en/vs/sem-vs-serum)
- **seem** (https://plainspell.com/en/vs/seem-vs-serum)
- **scum** (https://plainspell.com/en/vs/scum-vs-serum)
- **seam** (https://plainspell.com/en/vs/seam-vs-serum)
- **Sera** (https://plainspell.com/en/vs/sera-vs-serum)
- **Serb** (https://plainspell.com/en/vs/serb-vs-serum)
- **Seri** (https://plainspell.com/en/vs/seri-vs-serum)
- **Seoul** (https://plainspell.com/en/vs/seoul-vs-serum)

## Common misspellings (7)
`esrum`, `sermu`, `serrum`, `serumm`, `seurm`, `sreum`, `sserum`

## Source
Compiled from Wiktionary via kaikki.org (CC BY-SA). Data vintage: 2026-05-06.
Canonical page: https://plainspell.com/en/word/serum