FWIW I'd take issue with certain elements of Dovster's description of separation of powers, though that's more a discussion for OMNI. Independently, "separation of powers" isn't a clear principle in the US constitution, and some prefer the "balance of power" metaphor.

(The two were squarely at issue in the Supreme Court case Morrison v. Olson challenging an independent counsel statute, in upholding the independent counsel the Court clearly came down on the 'balance of power' side of the issue...)