noun
A somewhat formal term for a written letter or note, often used in official or literary contexts. More formal than 手紙.
社長から書簡が届いた。
A letter arrived from the company president.
彼は定期的に書簡をやり取りしている。
He regularly exchanges correspondence.
手紙 is the common, everyday word for 'letter'. 書簡 is more formal and often used in business or literary settings.
Sino-Japanese compound of 書 (writing) and 簡 (simplified, brief), originally referring to a brief written message.