Onomatopoeia normally refers to "the formation of a word from a sound associated with what is named" (Source: Oxford Living Dictionaries). The English word beep, for instance, imitates the sound it denotes, and the word roar recreates the cry of a lion or a similar large wild animal.
There is a plethora of onomatopoeic words in the Japanese language. What makes these expressions so special, however, is their ability to convey a lot more than just sounds and noises. In fact, they can be divided into two large groups: giongo, i.e. words that mimic sounds, and gitaigo, i.e. words that mimic states of the external world. The latter group includes expressions that describe the way people laugh (e.g. nikoniko "to smile"), the way they sleep (e.g. utouto "to nod off"), or even the way they feel (e.g. gakkari "to be disappointed"). Gitaigo expressions are also used to depict natural phenomena (e.g kankan "scorching heat"), shapes of objects (e.g. dekoboko "uneven surface"), or movement (e.g. yochiyochi "to toddle").
For this blog post, I have decided to focus on a rather narrow category of onomatopoeic expressions that describe rain. Most of the words listed below can be classified as giongo, i.e. words that mimic sounds or noises. The list serves to demonstrate just how differently a particular sound can be perceived and reproduced in a different linguistic environment. (Also, the rainy season is just around the corner in Japan, so I think this topic is quite appropriate.)
This expression is used to describe the sporadic raindrops that you see (or feel) when it is just about to start raining.
"Shitoshito" denotes a gentle rain, heavier than a drizzle but not quite as intense as a downpour.
When rain falls in large drops, it rains "botabota." This word mostly refers to the repeated sounds the heavy raindrops make as they hit a surface.
This onomatopoeic expression is used to describe raindrops that fall in scattered, irregular patterns.
As its sound may suggest, the word "zāzā" denotes continuous heavy rain.