serum

serum [sir′əm]

n.

pl. serums or sera [sir′ə] [L, whey < IE * serom, fluid < base * ser-, to flow > Sans sara-, fluid, Gr hormē, an attack]

1.

a) a clear, watery animal fluid, as serous fluid

b) the clear, yellowish fluid of the blood which separates from a blood clot after coagulation and shrinkage: in full blood serum

2. blood serum containing agents of immunity, taken from an animal made immune to a specific disease by inoculation: it is used as an antitoxin and for diagnosis

3. the whey of milk

4. the thin, watery part of a plant fluid