serum
Serum (noun) means a thin, lightweight skincare product, usually applied after cleansing and before a heavier cream, formulated to carry a high proportion of active ingredients in a small amount of liquid. Example: “She kept the serum on the shelf above the sink and used it before her moisturiser.”
How to use serum
Learner’s notesIn plain EnglishEither a thin, strong-smelling skin liquid you put on before cream, or the clear part of blood left after it clots.
The skincare sense is everyday; the blood senses are technical and belong to medicine and laboratory science. The plural is serums or, in scientific writing, sera.
Context decides the meaning entirely: on a bathroom shelf it is a cosmetic, in a hospital report it is a blood fraction.
Trace the full origin ↓Fill the gap
Can you complete this real example?
She kept the _____ on the shelf above the sink and used it before her moisturiser.
Etymology
From Latin serum, meaning whey or watery fluid.
Synonyms
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Frequently asked questions
What is the difference between a serum and a moisturiser?
A serum is thin and is built to deliver a concentrated dose of specific ingredients; a moisturiser is generally richer and is built to soften the skin and slow water loss from its surface. They sit at different points in a routine, with the lighter serum going on first.
Is serum the same as plasma?
No. Plasma is the liquid part of blood including the clotting proteins; serum is what remains after blood has clotted, so the clotting proteins are gone. Laboratories treat the two as different sample types.
Why are serums sold in such small bottles?
Because they are concentrated and are applied in very small amounts, often a few drops. Bottle size reflects how the product is dosed rather than how long it lasts.
What is the meaning of serum?
"serum" (noun) means a thin, lightweight skincare product, usually applied after cleansing and before a heavier cream, formulated to carry a high proportion of active ingredients in a small amount of liquid.