serum

1 of 2

noun

se·​rum ˈsir-əm 

plural sera ˈsir-ə  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

serum

2 of 2

adjective

: 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

Noun

Sunday Riley’s brightening serum offers benefits that keep on building. —Jenny Berg, Vogue, 22 Apr. 2024

Use a conductive serum first and then begin to glide the tool in gentle motions. —Alyssa Grabinski, Peoplemag, 19 Apr. 2024

The serum delivers multiple active ingredients to the skin without causing any sort of irritation or disruption. —Danielle Cohen, Glamour, 10 Apr. 2024

Other finds include a high-tech hair dryer for 45 percent off and the viral hydrating Snail Mucin face serum for just $17. —Amber Love Bond, Travel + Leisure, 6 Apr. 2024

The serum is formulated with No7's proprietary, patent-pending peptide technology, Pepticology, which promotes the skin's self-repair process. —Annie Blackman, Allure, 3 Apr. 2024

Since salicylic acid can irritate skin, the serum is formulated with a water-soluble salicylic acid that still decongests skin and refines the appearance of pores without drying or stressing out skin. —Celia Shatzman, Forbes, 29 Mar. 2024

The serum is too harsh for thousands of the brand’s preadolescent fans — the exact demographic that founder Eisenman said has been buying more in the past six months, helping drive Bubble’s expansion into 12,000 stores in the US and the UK. —Jeannette Neumann, Fortune, 10 Apr. 2024

Editor's Tip: Allure commerce writer Jennifer Hussein says this serum is her go-to when her complexion looks more uneven than usual. —Jennifer Hussein, Allure, 10 Apr. 2024

Adjective

Lizzo completes her skincare process with a serum facial sheet mask from Cicapair. —Charmaine Patterson, Peoplemag, 24 Oct. 2022

Word History

Etymology

Noun

borrowed from Latin, "whey, wheylike fluid," of uncertain origin

Note: Latin serum has been conventionally linked with Greek orós, of identical meaning, and both compared with the Sanskrit verbal base sar-, allegedly meaning " flow" in Vedic texts (hence P. Chantraine in Dictionnaire étymologique de la langue grecque). More recently, however, this interpretation has been rejected, and sar- read as "run off"—hence Vedic Sanskrit ásarat "ran off," prasísarti "lets run, stretches, extends," not akin to sáraḥ "lake, pond" and related words, which describe still water. The Sanskrit etymon has been further compared with Greek hállomai "(I) spring, hop," Latin salīre "to jump" (see sally entry 2). If this is correct the Indo-European base is *sel-, and any connection to serum and orós impossible; these two words are left then without any certain etymology.

Adjective

from attributive use of serum entry 1

First Known Use

Noun

1651, in the meaning defined at sense 1

Adjective

1876, in the meaning defined above

Phrases Containing serum

• blood serum
• convalescent serum
• serum albumin
• serum globulin
• serum hepatitis
• serum sickness
• truth serum

Kids Definition

serum

noun

se·​rum

ˈsir-əm

plural serums or sera

ˈsir-ə

1

: blood serum

2

: antiserum

Medical Definition

serum

1 of 2 noun

se·​rum ˈsir-əm 

plural sera -ə  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)

: antiserum

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