Hemostasis is ""the process which spontaneously arrests the flow of blood from vessels carrying blood under pressure. It is accomplished by contraction of the vessels, adhesion and aggregation of formed blood elements (e.g. erythrocyte aggregation), and the process of blood coagulation."[1]
Hemostasis consists of coagulation and platelet activation.
For medical purposes, hemostasis can be inhibited by anticoagulanta or platelet aggregation inhibitors.