Control

A control is anything you put in place to make something less likely to go wrong, or less bad when it does. A lock, a backup, an approval step, a check in some software.

The word gets used loosely, and that is where trouble starts. A control that exists on paper is not the same as one that is switched on, and one that is switched on is not the same as one that is working. Plenty of organisations discover during an incident that the thing they were relying on had been quietly failing for months, and nobody noticed because nobody was checking that the checker still worked.