I just saw this from a person who really should know better:
“[When XXX happens], you’ve got to reign them in.”
Unfortunately, it’s all too common a mistake. Sorry, no. You’ve go to rein them in. I suppose an argument could be made that you’ve got to rule them, and a rule is a reign, but it’s a pretty hollow argument.
Reign
- period of rule: the period of time during which somebody, especially a king or queen, rules a nation
- control or influence: the fact of being the dominant or controlling power or factor in something, or the period of time during which this dominance persists
- rule a nation: to exercise sovereign power or a controlling influence over something, especially to rule a country as its king or queen
Rein
- strap for controlling a horse (or another animal): a strap, or each half of a strap, by which a horse is controlled by its rider or by the driver of a coach or cart it is pulling
- exercise of power: any means of guiding, controlling, or restraining somebody or something
(Definitions adapted from Encarta)






