Which agglutinogens you have on your erythrocytes defines your blood type.
你红细胞上的凝集素决定了你的血型。
Crash Course 解剖生理学篇
Your red blood cells have specialized antigens on them, called agglutinogens, that activate antibodies that work by binding invading cells to each other, which causes coagulation, or the clumping of blood.
In the most important blood classification — the kind people are most familiar with — there are only two kind of agglutinogens, simply A and B. And your blood can either have one, or both, or neither of these molecules.