General "letter":
* 手紙 (tegami): This is the most common word for "letter" and refers to a written message, typically sent through the mail.
Letter as in alphabet:
* 文字 (moji): This means "character" or "letter" in the sense of the alphabet.
* アルファベット (arufabeto): This is the Japanese word for "alphabet."
Letter as in a formal document:
* 文書 (monjo): This refers to a formal document or written communication.
Other specific types of letters:
* 郵便 (yūbin): This refers to a letter sent through the postal service.
* 手紙 (tegami): This can also be used for a letter to a loved one or a personal letter.
So, the best way to say "letter" in Japanese depends on the specific context. If you're unsure, "手紙 (tegami)" is a safe bet for most situations.