O型 (Blood) is one of the four main blood types in the ABO blood group system, characterized by the absence of A and B antigens on the surface of red blood cells. Individuals with O型 blood can donate to any other blood type, making them universal donors. However, they can only receive blood from other O型 donors. This blood type is prevalent in many populations worldwide, with varying frequencies. O型 blood is important in medical settings, especially during emergencies when blood transfusions are needed. Understanding blood types, including O型, is crucial for safe blood transfusions and organ transplants.