We’ve all used and/or heard the expressions “free rein,” “rein it in,” and “take the reins.” All of them use the word “rein,” which can be a noun or a verb. Reins are the straps attached to a horse or other animal’s headgear. A rider uses reins to control and steer the animal. But these phrases also are used as expressions in daily life and work outside of the equine world. 

The homophone “reign” means to rule with power and authority. It’s mostly used with sovereigns, like kings and queens but has been extended to sometimes be used in the context of other leaders such as those in businesses. Example: Stephanie Conner reigns over Active Voice. Long live the Queen!