In spoken English, the words rain, rein, and reign all sound alike. Each can be used as a noun or as a verb.
Rain, of course, falls from the sky, just as other objects can rain down. Horses can be reined in or given free rein, as can emotions and people. Rulers reign, and their reign may be characterized by a particular quality or feature; that quality can also be said to reign. (The Reign of Terror occurred during the French Revolution.)
(noun): The forecast calls for rain this evening.
The rains came early that year.
(verb) Don’t rain on my parade!
Debris from the explosion rained upon the unsuspecting crowd.
(noun): Grab hold of the reins!
With free rein to experiment, the team developed innovative designs.
(verb): Rein in your goons, please.
Rein your horse as needed.
(noun): During his reign, peace prevailed.
The reign of tyranny must end!
(verb): Chaos reigns supreme.
She reigned at a time of great change.
When you understand the differences, you will not only know how to use each word correctly, you might also devise humorous or satirical titles, headlines, or phrases.
The Reign of Error
The queen rains on plans for a palace party.
Is the rain still free?