Writing paper used for letters; often used together with an envelope.
遠くに住む友だちに便箋で手紙を書いた。
I wrote a letter on writing paper to a friend who lives far away.
便箋に一言添えてプレゼントを渡した。
I attached a short note on writing paper and handed over the present.
文房具店でかわいい便箋を見つけた。
I found some cute writing paper at the stationery store.