Checks and balances
Etymology
The phrase joins “check” and “balance.” “Check” comes, remarkably, from chess: via Old French from Persian “shah,” “king” — the warning “check” meant the king was under threat, and “checkmate” is from “shah mat,” “the king is helpless.” From threatening the king came the sense of stopping or restraining. “Balance,” from Latin “bilanx,” “two-panned scale,” adds the image of forces held in equilibrium.
noun phrase · /CHEKS and BAL-un-siz/
Mechanisms by which each branch of government can limit and correct the others, so no one part dominates.
What it names
Reach for it to name the machinery that turns separated powers into mutual restraint — the veto, the override, the judicial strike-down.
Example
The legislature’s power of the purse is one of the sharpest checks and balances on the executive.
Related idea
Separation of powers divides government into distinct branches; checks and balances is what lets those branches police one another. The first draws the boundaries; the second arms each side to defend them, so that ambition is made to counter ambition.