What is and example of a city-state?

a multi state nation is a nation that crosses over country borders. i.e. kurdistan a nation that crosses over parts of the Middle East, georgia, Armenia etc

Additional answer

The US is an example of a nation which has many states, and is therefore a multistate nation. The United Kingdon could be called a multinational state. But if you, the questioner, really means what you say in the question then the US is your prime example.