Rein and reign are easily confused words.
The spell-check application of most word processing software programs would not catch a slip-up of these two words. Spell-check is looking for words that aren’t in its dictionary, and words that resemble words in its dictionary but are possibly spelled wrong. Spell-check isn’t perfect. It doesn’t know and can’t guess what word you wanted or what word you meant, it can only judge the words on the page. If you used words that are all spelled correctly, it gives you a pass anyway.
Autocorrect suggests words that start with the same letters. It suggests what word you may want to save time, but quite often, its suggestions couldn’t be more off base and produces humorous results.
Rein is a noun. It means the leather straps attached to a horses bridle that are used to guide the horse’s direction, so the rider can tell the horse to speed up, veer left, veer right, slow down, or stop. Typically the rider is also speaking to the horse with specific words in unison with the reins’ motion.
Figuratively, “taking the reins” is the same as “taking the wheel”. Both phrases mean to take control or charge of something, like a big project, because the current person is incapacitated, or has completely lost interest.
Reign is a noun. It means the ruling time period for an emperor, king/queen, or other monarch. Right now, the UK is in the reign of Elizabeth II. Japan is in the reign of Emperor Akihito. Sweden is in the reign of Carl XV Gustaf, Netherlands is in the reign of Willem-Alexander.
The following story uses both words correctly:
Rainier’s brother abdicated the throne. He ended his reign abruptly because his new foreign lover would never be accepted as a royal. Though he didn’t love the spotlight, his younger brother Rainier took the reins of responsibility and ascended to the throne. Rainier and Queen Carmen Marguerite reigned during a particularly turbulent period in its history. Every king must be honored and served in their time, but Rainier’s people actually seemed to love him and have tremendous faith in his leadership.
This post is related to another one: Rain vs. Reign.