Hemolysis or haemolysis (from the Greek (aima, haema, ) meaning "blood" and (lusis, , ) meaning a "loosing", "setting free" or "releasing"), is the rupturing of erythrocytes (red blood cells) and the release of their contents (cytoplasm) into surrounding fluid (e.g. blood plasma). Hemolysis may occur in vivo or in vitro (inside or outside the body).