Meanings
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1
noun
the clear, pale fluid that remains after blood has clotted and blood cells and clotting proteins have been removed
The laboratory tested the patient's serum for antibodies.
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2
noun
serum containing antibodies, used in diagnosis, research, or treatment to provide passive immunity
The clinic administered an antitoxin serum after the exposure.
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3
noun
a light skin-care preparation containing a concentrated active ingredient
She applied a vitamin C serum before moisturizer.
Thesaurus
Etymology
Borrowed from Latin serum, 'whey.' Scientists applied the word to the clear liquid that separates from clotted blood because it resembles the watery portion of milk. Medical compounds such as antiserum preserve that biological sense.