The Nazis distinguished between extermination and concentration camps. The terms "extermination camp" ("Vernichtungslager") and "death camp" ("Todeslager") were interchangeable in the Nazi system, each referring to camps whose primary function was genocide. Six camps meet this definition, though extermination of people happened at every sort of concentration camp or transit camp; the use of the term extermination camp with its exclusive purpose is carried over from Nazi terminology. The six camps were Chelmno, Belzec, Sobibor, Treblinka, Majdanek and Auschwitz (also called Auschwitz-Birkenau).