Cambridge Dictionaries online Cambridge Dictionaries online

The most popular online dictionary and thesaurus for learners of English


English definition of “serum”


noun [C or U] (BLOOD)    /ˈsɪə.rəm/ US  /ˈsɪr.əm/ (plural sera   /ˈsɪə.rə/   US  /ˈsɪr.ə/ or serums)
the thin yellowish liquid part of the blood : cholesterol levels in blood serumThe circulatory system and blood serum taken from an animal's blood and put into a human in order to fight an infection or a poison : an anti-venom serum
(Definition of serum noun (BLOOD) from the Cambridge Advanced Learner's Dictionary & Thesaurus © Cambridge University Press)
Focus on the pronunciation of serum

More definitions for “serum”

Definitions of “serum” in other dictionaries

Word of the Day

prenuptial agreement

an official document signed by two people before they get married that says what will happen to their possessions and/or children if they divorce (= officially stop being married)

Word of the Day


Read our blog about how the English language behaves.

Learn More

New Words

Find words and meanings that have just started to be used in English, and let us know what you think of them.

Learn More