Rain is part of the water cycle, in which "rain falls from the clouds, evaporates, and turns into moisture in the air, which then condenses to form new clouds and thus begins the cycle once again." Rain is composed of droplets of water called raindrops.
Water falling from the atmosphere as rain, snow, sleet, or hail.
The Hydrological Cycle
Scientifically speaking, rain is a form of precipitation.
Rain in Poetry and Song
- Love is but a song we sing, fear's the way we die; you can make the mountains ring or make the angels cry." ("Let's Get Together", Chet Powers)
- The Fairy Glade 
- Wile, Dr. Jay L. Exploring Creation With Physical Science. Apologia Educational Ministries, Inc. 1999, 2000