Sepsis (in Greek Σήψις, putrefaction) is a serious medical condition caused by a severe infection. The more critical subsets of sepsis include severe sepsis (sepsis with acute organ dysfunction) and septic shock (sepsis with refractory arterial hypotension). If a proven source of infection is lacking but the other criteria of sepsis are met the condition typically meets the criteria for systemic inflammatory response syndrome (SIRS); the exception is the condition greater than 10% band forms (this is not a part of the SIRS definition).