Reign and rein sound alike, but they mean very different things.
Reign is about ruling, power, or authority. It is used for kings, queens, leaders, or even periods of dominance. For example, The queen will reign for years.
Rein is the strap used to control or guide a horse. It also appears in figurative expressions such as rein in, which means to control or limit something. For example, Pull the left rein gently. You could also say, The company needs to rein in spending.
A quick way to remember the difference is this: reign relates to rulers, while rein relates to steering and control.
- Use reign for rule, power, or dominance.
- Use rein for horse tack or for controlling something.
If you are talking about authority, choose reign. If you are talking about guiding, restraining, or controlling, choose rein.