1.NounThe science that studies the blood serum, and especially the reaction between antigens and antibodies in serum.
2.NounThe characteristics of the blood serum in a particular disease or organism.
3.NounA serologic test: a blood test to detect the presence of, and often to measure the amount of, various components of the serum (usually antibodies, antigens, and immune complexes thereof).
"Diagnosis is presumptive by history and physical examination and is confirmed by serologies."