blood: the life-fluid of a body, and by extension a life violently taken or a death that brings cleansing
Across the New Testament one word, blood, carries a range that runs from the plainly physical to the deeply theological, and the senses are linked by a single idea inherited from the Old Testament: blood is where life is. Because the life of a creature is bound up in its blood, to shed blood is to take a life, and to offer blood is to offer a life in another's place.
So the literal fluid (a wound, a hemorrhage, water turned to blood) sits alongside blood as a way of naming violent death and the guilt that clings to those who cause it. From the same root grows the most weighted use of all: the blood of sacrifice, and above all the blood of Jesus, the poured-out life that the New Testament says cleanses, ransoms, and seals a new covenant.
A fourth use is idiomatic. Paired with flesh, blood stands for ordinary human nature in its frailty, as opposed to God or to spiritual powers. Here blood is not a substance at all but a shorthand for what it is to be merely human.
The reader should hold these together rather than collapse them. When the New Testament speaks of the blood of Christ it is not describing a liquid; it is naming a death, understood as a life laid down.