ABO System:

The ABO System is a classification system used to categorize human blood types based on the presence or absence of certain antigens on the surface of red blood cells (RBCs). This system is widely used in blood transfusion and transplantation to ensure compatibility between donors and recipients. The ABO blood group is determined by the combination of two main antigens, A and B, and the presence or absence of antibodies against these antigens in the plasma.