plural sera
ˈsir-ə 
or serums
or serums
1
: the watery, clear portion of an animal fluid:
a
: the clear, yellowish fluid that remains from blood plasma after clotting factors (such as fibrinogen and prothrombin) have been removed by clot formation : blood serum compare antiserum, convalescent serum
b
: a normal or pathological serous fluid (as in a blister)
c
: whey
2
: a usually lightweight cosmetic preparation especially for use on the face
specifically
: a typically water-based, often concentrated preparation that lacks lubricating and thickening agents
an antiaging facial serum
3
: the watery part of a plant fluid
Latex. This, the natural product of the rubber tree, is a suspension of rubber droplets in a watery serum concentrated and stabilized in such a way that the dry rubber content is between 60 and 70 per cent.—
C. A. O'Flaherty
see also truth serum
C. A. O'Flaherty
: occurring or found in the blood serum
serum cholesterol
serum antibodies
Examples of serum in a Sentence
Noun
The patient was administered serum.
Recent Examples on the Web
Conçetta Ciarlo, Vogue, 22 Nov. 2024
From the tumbler to the serum, which was among the products that made their debut when the brand launched in 2021, the kit has glam written all over it.
—Jackie Fields, People.com, 4 Nov. 2024
Charmaine Patterson, Peoplemag, 24 Oct. 2022
See all Example Sentences for serum 
Examples are automatically compiled from online sources to
show current usage.
Read More
Opinions expressed in the examples do not represent those of Merriam-Webster or its editors.
Send us feedback.
Noun
Beauty of Joseon has quickly gained popularity as a beloved Korean brand, boasting some of the best K-Beauty serums.
—Conçetta Ciarlo, Vogue, 22 Nov. 2024
From the tumbler to the serum, which was among the products that made their debut when the brand launched in 2021, the kit has glam written all over it.
—Jackie Fields, People.com, 4 Nov. 2024
Adjective
Lizzo completes her skincare process with a serum facial sheet mask from Cicapair.
—Charmaine Patterson, Peoplemag, 24 Oct. 2022
See all Example Sentences for serum
Dictionary Entries Near serum
Cite this Entry
“Serum.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/serum. Accessed 1 Dec. 2024.
Copy CitationMedical Definition
serum
1 of 2 noun
se·rum
ˈsir-əm
plural sera
-ə
or serums
or serums
: the watery portion of an animal fluid remaining after coagulation:
a(1)
: the clear yellowish fluid that remains from blood plasma after fibrinogen, prothrombin, and other clotting factors have been removed by clot formation
called also blood serum
(2)
b
: a normal or pathological serous fluid (as in a blister)
serum
2 of 2 adjective
: occurring or found in the serum of the blood
serum cholesterol
serum glutamic-oxaloacetic transminase
Love words? Need even more definitions?
Merriam-Webster unabridged
Share