German reunification (German: Deutsche Wiedervereinigung) was the process in 1990 in which the German Democratic Republic (GDR, colloquially East Germany; German: Deutsche Demokratische Republik/DDR) became part of the Federal Republic of Germany (FRG, colloquially West Germany; German: Bundesrepublik Deutschland/BRD) to form the reunited nation of Germany, and when Berlin reunited into a single city, as provided by its then Grundgesetz (constitution) Article 23. The end of the unification process is officially referred to as German unity (German: Deutsche Einheit), celebrated on 3 October (German Unity Day) (German: Tag der deutschen Einheit). Following German reunification, Berlin was once again designated as the capital of united Germany.
The 1945 Potsdam Agreement had specified that a full peace treaty concluding World War II, including the exact delimitation of Germany's postwar boundaries, required to be "accepted by the Government of Germany when a government adequate for the purpose is established." The Federal Republic had always maintained that no such government could be said to have been established until East and West Germany had been united within a free democratic state; but in 1990 a range of opinions continued to be maintained over whether a unified West Germany, East Germany, and Berlin could be said to represent "Germany as a whole" for this purpose. The key question was whether a Germany that remained bounded to the east by the Oder–Neisse line could act as a "united Germany" in signing the peace treaty without qualification. Under the "Two Plus Four Treaty" both the Federal Republic and the Democratic Republic committed themselves and their unified continuation to the principle that their joint pre-1990 boundaries constituted the entire territory that could be claimed by a Government of Germany, and hence that there were no further lands outside those boundaries that were parts of Germany as a whole.
The post-1990 united Germany is not a successor state, but an enlarged continuation of the former West Germany. As such, the enlarged Federal Republic of Germany retained the West German seats in international organizations including the European Community (later the European Union) and NATO, while relinquishing membership in the Warsaw Pact and other international organizations to which only East Germany belonged. It also maintains the United Nations membership of the old West Germany.
For political and diplomatic reasons, West German politicians carefully avoided the term "reunification" during the run-up to what Germans frequently refer to as die Wende. The official and most common term in German is "Deutsche Einheit" ("German unity"); this is the term that Hans-Dietrich Genscher used in front of international journalists to correct them when they asked him about "reunification" in 1990.
After 1990, the term "die Wende" became more common. The term generally refers to the events (mostly in Eastern Europe) that led up to the actual reunification; in its usual context, this term loosely translates to "the turning point", without any further meaning. When referring to the events surrounding reunification, however, it carries the cultural connotation of the time and the events in the GDR that brought about this "turnaround" in German history. However, anti-communist activists from Eastern Germany rejected the term Wende as it was introduced by SED's (Sozialistische Einheitspartei Deutschlands, Socialist Unity Party of Germany) Secretary General Egon Krenz.