Synonyms: country, land, nation state, state
A certain amount of flexibility is needed when interpreting this definition. Is the European Union a nation? Possibly, although the constituent states are generally considered to be nations too. Is a city a nation, when it has its own local government? Not if it's part of a larger territory considered to be a nation. Can't we just use a United Nations list of countries? No, since we'd like to refer to nations that disappeared before the UN was created, or nations that are not recognised as such by the UN.
"Nation" is also used in other cases which don't meet the definition above: