ain作名词表示雨：Rain is water that falls from the clouds in small
drops.
rain作不及物动词表示下雨：I think it's going to rain.
the rains表示雨季：The rains is coming.
rain作动词时的第三人称单数也是rains：it rains heavily.
rainy是形容词 下雨的；多雨的：The rainy weather would hold for a week.多雨的天气将会持续一周
rain做及物动词表示 厚施,大量地给,此时过去式就是rained：They rained flowers on the head of the bride.他们将鲜花撒在新娘头上.