A polite adverb meaning 'truly' or 'indeed'; often used in formal or written contexts (e.g., 誠にありがとうございます).
誠にありがとうございます。皆さんのおかげです。
Thank you very much. It's thanks to all of you.
誠に残念ですが、本日のイベントは中止となりました。
It is truly unfortunate, but today's event has been canceled.
誠に申し訳ありませんが、ただいま担当者が不在です。
We are truly sorry, but the person in charge is currently absent.