rainfall
n. uncountable B1 Intermediate US //ˈɹeɪnˌfɔɫ// UK //ɹˈeɪnfɔːl// rain·fall
n. the total amount of rain that falls in a specific place during a certain time.
n. the quantity of water, expressed in depth or volume, falling as rain within a given area and time period.
The heavy rainfall caused the river to overflow.
Farmers are worried because the annual rainfall has been much lower than average this year.
Tropical rainforests maintain their lush biodiversity through consistent year-round rainfall, which facilitates the rapid nutrient cycling necessary for such dense vegetation to thrive.
From rain + fall.
Pitfall
The rainfalls were very heavy yesterday.The rainfall was very heavy yesterday.Learners often pluralize 'rainfall' when describing a single weather event, but it should remain singular as an uncountable noun.