n A vital liquid flowing in the bodies of many types of animals that usually conveys nutrients and oxygen. In vertebrates, it is colored red by hemoglobin, is conveyed by artery|arteries and veins, is pumped by the heart and is usually generated in bone marrow.
n A family relationship due to birth, such as that between siblings; contrasted with relationships due to marriage or adoption. (See blood relative, blood relation, by blood.)