rain·fall  (rān′fôl′)
n.
1. A shower or fall of rain.
2. The quantity of water, expressed in inches, precipitated as rain, snow, hail, or sleet in a specified area and time interval.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
rainfall (ˈreɪnˌfɔːl)
n
1. (Physical Geography) precipitation in the form of raindrops
2. (Physical Geography) meteorol the amount of precipitation in a specified place and time