Which amendment reserves powers not prohibited by the Constitution to the states?

The Tenth Amendment is significant because it clearly delineates the balance of power between the federal government and the states. Specifically, it states that powers not granted to the federal government nor prohibited to the states by the Constitution are reserved for the states or the people. This foundation of federalism is crucial for the way governance is structured in the United States, as it allows states to exercise authority over matters not explicitly outlined in the Constitution. This includes areas such as education policies, local law enforcement, and other state-level issues, thereby allowing for diversity of governance that accommodates the various needs and preferences of different states.