The term German Empire (German: Deutsches Kaiserreich) commonly refers to Germany, from its foundation as a unified nation-state on January 18, 1871, until the abdication of its last Kaiser, Wilhelm II, on November 9, 1918. Germans, when referring to the Reich in this period under the Kaisers, typically use the term Kaiserreich and this term has often been used by non-German historians.
Sometimes in English, but rarely in German, the name Second Reich is used, based on counting the Holy Roman Empire of the German Nation as the first German empire and Nazi Germany as the third. Numbering of the Reichs began in 1923 by Arthur Moeller van Den Bruck (he longed for a third, which he idealized) and was briefly taken up by Nazi propaganda. After the 'Great war' (later known as First World War), Drittes Reich ('Third Empire', often semi-translated as 'Third Reich') became the standard name for Nazi Germany, used by Hitler's regime itself.
It should be noted that Deutsches Reich was the state's official name not only in the period of the Kaisers 1871 to 1918, but also during the Weimar Republic, and in Nazi Germany;