rainfall
Word family
Synonym discussion
Sense: noun/1
Rain, precipitation, and rainfall all describe water falling from the sky, but they differ in register and scope. Rain is the most common, everyday word — you would use it in casual conversation ('It looks like rain today'). Precipitation is a formal, technical term that covers all forms of water falling from the atmosphere (rain, snow, sleet, hail); it belongs in weather reports and scientific writing. Rainfall sits between these two — it is less technical than precipitation but more formal and measured than plain rain, often used when discussing totals or averages ('annual rainfall'). Downpour refers to a single, very heavy rain event, not a general condition. Drizzle is the opposite — light, fine rain with very small drops. For example, 'The weekly rainfall total was 50 mm' would sound oddly vague with 'rain' and overly formal with 'precipitation', while 'A sudden downpour soaked the hikers' is more natural than 'a sudden heavy rainfall soaked the hikers.'
Common collocations
Etymology
Rainfall is a compound word formed from 'rain' (from Old English regn) and 'fall' (from Old English feallan). The two words were first written together as a single noun in the mid-1800s, when scientists and meteorologists needed a precise term for the measured amount of rain in a given area over a set period.