noun
contained in a letter; stated in a letter
Used in formal or written contexts to refer to something that is written or contained within a letter. Often appears in phrases like 書中にて or 書中に記載の通り.
詳細は書中にてご確認ください。
Please check the details in the letter.
書中に記載の通り、会議は延期となりました。
As stated in the letter, the meeting has been postponed.