Okay, people, the next spelling and grammar lesson of the day. Today's lesson is with homonyms, or each of two words having the same pronunciation but different meanings, origins or spellings.
With that said, rain, rein and reign are all different words, with different meanings and, hence, different usages:
rain = water falling from the sky
rein = a strap used with horses
reign = the length of time a leader rules
Saying, "turn over the reigns" makes no sense.