also: かっぱ
A waterproof coat worn in the rain; from Portuguese 'capa'.
from Portuguese capa
It started raining, so I put on my raincoat.
It looks like rain, so let's take a raincoat.
When I was a child, I wore a yellow raincoat to school.
I threw on my raincoat before getting on my bike.
雨具 is a broad term covering any rain-protection gear (umbrellas, boots, coats), while 合羽 refers specifically to the coat itself.
蓑 is a traditional straw raincoat worn in pre-modern Japan, while 合羽 refers to a modern raincoat made of waterproof fabric.
河童 (also read かっぱ) is the mythical water creature of folklore, completely unrelated in meaning to 合羽 the raincoat despite sharing the same pronunciation.
Katakana spelling is standard for this loanword; usually written in kana.
Hiragana variant, less common than katakana but still encountered.
Ateji spelling; rarely used in modern writing.
From Portuguese 'capa' (cloak, cape). The ateji spelling 合羽 is a phonetic rendering.