This is the 1514th most frequent Chinese word.
联合国
United Nations.
Here, '联合国' is used to refer to the organization itself.
联合国在国际事务中扮演重要角色。
The United Nations plays an important role in international affairs.
In this context, '联合国' denotes the entirety of its operations and missions.
我们应该支持联合国的和平使命。
We should support the peace missions of the United Nations.
This highlights a specific aspect or division of the '联合国', referring to one of its major assemblies.