Translation guide
The top administrative officer of an organization, especially the United Nations. In Japanese, the term is usually a direct translation, but usage depends on the specific organization.
国連事務総長
UN Secretary-General
The head of the secretariat of an international body like the UN, NATO, etc.
Standard translation for 'secretary-general' of international organizations, especially the United Nations.
国連事務総長は平和維持に尽力している。
The UN Secretary-General is working hard for peacekeeping.
Used for 'secretary-general' in some political parties or unions, but can also refer to a chief secretary. Less common for international organizations.
彼は党の書記長に選ばれた。
He was elected secretary-general of the party.
The top official of a particular international body, often with a title that includes the organization's name.
Common pattern for 'secretary-general' of many organizations, using 事務局長 (head of secretariat).
OPEC事務局長は会議で発言した。
The OPEC Secretary-General spoke at the meeting.
Sometimes used alone when the organization is clear from context, but less specific.
総長は来月退任する。
The secretary-general will step down next month.
事務総長 is the standard term for the UN and most international organizations. 書記長 is used for political parties (e.g., Communist Party) or some unions, and can also mean 'chief secretary' in other contexts.