A written message sent to someone, typically on paper and enclosed in an envelope. It's a traditional way to communicate over distance, conveying news, thoughts, or information to a recipient.

相手(あいて)に伝(つた)えるために、紙(かみ)に書(か)かれたメッセージ。封筒(ふうとう)に入(い)れて送(おく)る。