What is the meaning of Serology?

The science that studies the blood serum, and especially the reaction between antigens and antibodies in serum.

The characteristics of the blood serum in a particular disease or organism.

A 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).

Source: wiktionary.org