Secretariat (administrative office)

The secretariat of an international organization is the department that fulfils its central administrative or general secretary duties. The term is especially associated with governments and intergovernmental organizations such as the United Nations, although some non-governmental organizations (for example, the International Organization for Standardization) also refer to their administrative department as their secretariat.

Source: Wikipedia — Secretariat (administrative office) (CC BY-SA 4.0)