rained / reigned / reined are similar-sounding terms with different meanings (referred to as homophones). To better understand the differences, see below for definitions, pronunciation guides, and example sentences using each term. 👇
rained: (verb) precipitate as rain.
reigned: (verb) have sovereign power.
reined: (verb) stop or slow up one's horse or oneself by or as if by pulling the reins. (verb) stop or check by or as if by a pull at the reins.
rained: r·EY·n·d
reigned: r·EY·n·d
reined: r·EY·n·d
(Examples are Wikipedia snippets under the CC ShareAlike 3.0 license. Definitions drawn from WordNet.)