Sē'rum, n.

n. [Lat., allied to Gr. ὀρός, or ὀρρός.] (Physiol.) (a.) The liquid portion of the blood, after the separation of the coagulum or clot, of which albumen is the principal organic ingredient. (b.) A fluid of similar nature exuded from the blood-vessels.

Serum of milk, the whey, or that which remains after the removal of the caseine and butter.