A “government” is an established system of political administration. For example,
- the U.S. government
A “junta” is a group or council that often rules after a coup. For example,
- A military junta controls this region.
A junta becomes a government after is establishes a system of political administration.
The word “regime” is a synonym for “political system.” For example,
- a democratic regime
- an authoritarian regime
It may also mean the period in which a person or system was in power, often with a negative connotation. For example,
- Saddam Hussein’s regime
- the Nazi regime
An administration consists of officials who make up the executive branch of a government. For example,
- the Obama administration