serum

American  

[seer-uhm] / ˈsɪər əm /

noun

plural

serums, sera

1. the clear, pale-yellow liquid that separates from the clot in the coagulation of blood; blood serum.

2. immune serum.

3. any watery animal fluid.

4. the thin, clear part of the fluid of plants.

5. milk whey.

---

serum British  

/ ˈsɪərəm /

noun

1. See blood serum

2. antitoxin obtained from the blood serum of immunized animals

3. physiol zoology clear watery fluid, esp that exuded by serous membranes

4. a less common word for whey

---

serum Scientific  

/ sîr′əm /

plural

serums

1. See blood serum

2. Blood serum extracted from an animal that has immunity to a particular disease. The serum contains antibodies to one or more specific disease antigens, and when injected into humans or other animals, it can transfer immunity to those diseases.

---

Other Word Forms

• serumal adjective

Etymology

Origin of serum

1655–65; < Latin: whey

Example Sentences

After confirming that the device could detect miR-21 in a controlled buffer solution, they tested it using human serum from lung cancer patients to simulate an actual blood test.

From Science Daily • Feb. 16, 2026

Well, it's happened - and the gooey elasticity is key, according to a viral TikTok challenge promoting the serum.

From BBC • Jan. 2, 2026

After years of being mistakenly linked to high serum cholesterol, eggs were rolled out to the public as a “healthy” food by the FDA External link in December 2024 External link.

From Barron's • Dec. 11, 2025

As the YouTube hit demonstrates, hot sauce isn’t just for daredevils and masochists: It’s a truth serum.

From The Wall Street Journal • Nov. 20, 2025

He collected some blood from his patient and drew off the serum, which is a clear, golden-colored liquid that remains when the red cells are removed from the blood.

From "The Hot Zone" by Richard Preston

Related Words

• antibody