In general:
If
the title of an organizational body or agency occurs
frequently in a text, it should be written in full the first time (with its
abbreviation in parentheses). Thereafter, its abbreviation can be used in the
text, e.g., Office of Project Services (OPS).
However:
Some titles should never be abbreviated, even of they appear
frequently in the text. These are listed below
| the United
Nations |
| the United Nations Office at
Geneva |
| the United Nations Office at
Nairobi |
| the United Nations Office at
Vienna |
| the Economic and Social
Council |
| the General
Assembly |
| the
Secretary-General |
| the Security
Council |
While in everyday informal conversation (or in
e-mail messages), it is common for staff to use abbreviations of the above
titles (the UN, UNOG, UNOV, ECOSOC, the GA, the S-G, the S-C, the latter are NOT acceptable in formal correspondence).
Some United Nations acronyms are almost never
written in full: UNICEF, UNESCO