The system of government in ancient Greece and Rome was known as a "classical republic." It was a type of government where citizens had a say in how the country was run, but it was not a democracy in the modern sense of the word.

Government in Ancient Greece:

In ancient Greece, the city-state was the basic unit of government. The most famous city-states were Athens and Sparta. They had different forms of government. Athens had a democratic form of government, while Sparta had an oligarchic form of government.

- Athenian Democracy:
In Athenian democracy, all male citizens over the age of 18 could vote. Women, slaves, and foreigners were not allowed to vote. The government was run by a council of 500 citizens who were chosen by lottery. They served for one year and then were replaced by another group of citizens. The council was responsible for making laws and managing the government.

- Spartan Oligarchy:
In Sparta, the government was run by a small group of elites. This group was known as the "Council of Elders." They were responsible for making laws and managing the government. There was also a king who served as a figurehead. The citizens of Sparta had very little say in how the government was run.

Government in Ancient Rome:

Ancient Rome was a republic. The Roman Republic was founded in 509 BCE after the Romans overthrew their Etruscan conquerors. The government was run by two consuls who were elected by the people. They served for one year and then were replaced by another pair of consuls.

- Roman Senate:
The Senate was made up of 300 patricians (wealthy landowners). They were responsible for making laws and managing the government. The Senate was the most powerful branch of government.

- Roman Assemblies:
There were two types of assemblies in the Roman Republic. The first was the "Assembly of Centuries." This was made up of all male citizens over the age of 18. The second was the "Assembly of Tribes." This was made up of all male citizens regardless of their social class.

Conclusion:

In conclusion, the system of government in ancient Greece and Rome was a classical republic. It was a type of government where citizens had a say in how the country was run, but it was not a democracy in the modern sense of the word. In ancient Greece, the city-state was the basic unit of government. In ancient Rome, the government was run by two consuls and the Senate was the most powerful branch of government.

Ancient Greek and Rome had their federal structure of government. Later on they also monarchy and kingship
As the Greek were successfull in their democratic city state. The idea of republicanism was developed by the Romans.