# serum

/ˈsɪɹəm/ (US) · /sˈɛɹəm/ (UK)

Source: https://englishreference.com/word/serum
Updated: 2026-06-20

## Senses

### 1. skincare product

noun · CEFR B1

a liquid skin product that has a high concentration of active ingredients to help with specific problems like dryness or aging.

For teachers: a concentrated skincare formulation designed to deliver specific active ingredients deep into the skin.

- She applies a vitamin C serum every morning before using her moisturiser.
- Dermatologists often recommend a hyaluronic acid serum for patients with persistent skin dehydration due to its high water-retention properties.

### 2. blood component

noun · CEFR C1 · Technical

the clear, watery part of blood that remains after it has clotted.

For teachers: the clear yellowish fluid that remains from blood plasma after the fibrinogen has been removed during clotting.

- The lab technician separated the serum from the rest of the blood sample.
- The patient's serum was tested for specific antibodies to determine if they had developed immunity to the virus.

### 3. medical treatment

noun · CEFR C1 · Technical

a liquid taken from the blood of an immune animal or person, used to treat or prevent a disease.

For teachers: an antiserum containing antibodies used to provide passive immunity against a specific pathogen or toxin.

- Doctors administered an anti-venom serum immediately after the snake bite.
- Before the advent of modern antibiotics, researchers relied heavily on horse-derived serum to treat life-threatening bacterial infections like diphtheria.

## Examples

- She applies a vitamin C serum every morning.
- The doctor explained that the patient's serum levels showed a significant improvement after the new treatment.
- While traditional moisturisers focus on hydration through occlusive barriers, a serum typically contains smaller molecules that penetrate the epidermis more effectively to target specific dermatological concerns.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.