serum

noun

Etymology: Etymology tree Proto-Indo-European *ser- Proto-Indo-European *sér-o-der. Proto-Italic *serom Latin serumder. English serum From Latin serum (“whey”). Cognates include French sérum, Spanish suero, Italian siere, siero, Portuguese soro. Doublet of suero.

1. Ellipsis of blood serum.
2. Blood serum used as a blood product, in the practice of medicine: blood serum from the tissues of immunized animals (human or nonhuman), containing antibodies and used to transfer immunity to another individual (human or nonhuman).

   “Near-synonym: antiserum”

3. A watery liquid from animal tissue, especially one that moistens the surface of serous membranes or that is exuded by such membranes when they become inflamed, such as in edema or a blister.
4. The watery portion of certain other animal fluids, such as milk; whey.
5. A skincare product of varying consistencies with a high concentration of one or more active ingredients, for a targeted purpose, such as preventing acne, repairing sun damage, or moisturizing.