Answer:
There are three main systems of government: unitary, federal, and confederal. The fourth system that is sometimes mentioned is a hybrid system known as a "federation with a strong central government." This system combines elements of both federal and unitary systems of government, with power shared between the central government and regional or local governments, but with a stronger emphasis on central authority than in a typical federal system. However, this system is not as widely recognized or used as the other three main systems of government.