What is the separation of powers under

the U. S. Constitution?

It's called "checks & balances"

Explanation:

this is so 1 power cannot overrule the other.

example; the president can sign a law, but Congress has to approve in order to make it a law ...

Separation of powers is a doctrine of constitutional law under which the three branches of government (executive, legislative, and judicial) are kept separate. This is also known as the system of checks and balances, because each branch is given certain powers so as to check and balance the other branches.