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[seer-uh m] /ˈsɪər əm/
noun, plural serums, sera
[seer-uh] /ˈsɪər ə/ (Show IPA)
the clear, pale-yellow liquid that separates from the clot in the coagulation of blood; blood serum.
any watery animal fluid.
the thin, clear part of the fluid of plants.
milk whey.
Origin of serum
1655-65; < Latin: whey
Related forms
serumal, adjective Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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Examples from the web for serum
  • serum myoglobin is a test that measures the amount of myoglobin in the blood.
  • If you haven't already, get a serum ferritin test to check if the iron you are taking orally is being absorbed.
  • Human serum destroyed only eight of the bacterial strains.
  • serum immunoelectrophoresis is a test that measures immunoglobulins in the blood.
  • The researchers also looked at blood serum samples from human volunteers.
  • Little if anything has been published studying levels in serum or urine.
  • serum progesterone is a test to measure the amount of progesterone in the blood.
  • serum globulin electrophoresis is a laboratory test that looks at proteins called globulins in the blood.
  • serum cholinesterase is a blood test that looks at levels of two substances that help the nervous system work properly.
  • And, doctors who focus too narrowly on serum cholesterol may be overlooking.
British Dictionary definitions for serum


noun (pl) -rums, -ra (-rə)
antitoxin obtained from the blood serum of immunized animals
(physiol, zoology) clear watery fluid, esp that exuded by serous membranes
a less common word for whey
Derived Forms
serumal, adjective
Word Origin
C17: from Latin: whey
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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Word Origin and History for serum

1670s, "watery animal fluid," from Latin serum "watery fluid, whey," from PIE root *ser- (2) "to run, flow" (cf. Greek oros "whey;" Sanskrit sarah "flowing," sarit "brook, river"). First applied 1893 to blood serum used in medical treatments.

Online Etymology Dictionary, © 2010 Douglas Harper
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serum in Medicine

serum se·rum (sēr'əm)
n. pl. se·rums or se·ra (sēr'ə)

  1. A watery fluid, especially one that moistens the surface of serous membranes or that is exuded by such membranes when they become inflamed.

  2. The clear yellowish fluid obtained upon separating whole blood into its solid and liquid components.

  3. Such fluid from the tissues of immunized animals, containing antibodies and used to transfer immunity to another individual.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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serum in Science
Plural serums or sera
  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.

The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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