Truth; reality; the actual fact of something (somewhat literary or old-fashioned).
事件の誠を明らかにする必要がある。
It is necessary to clarify the truth of the incident.
彼はついに誠を述べ、誤解が解けた。
He finally told the truth, and the misunderstanding was resolved.
Sincerity, honesty, or faithfulness; acting with genuine, wholehearted intent.
彼女の誠が伝わり、信頼を得た。
Her sincerity came through and she gained trust.
誠を尽くして対応することが大切だ。
It's important to respond with all sincerity.
約束を守るのは誠のある人の行いだ。
Keeping promises is the behavior of a sincere person.
As an adverb (まことに), meaning 'truly' or 'indeed'; a somewhat formal or literary intensifier.
ご協力いただき、誠にありがとうございました。
Thank you very much for your cooperation.
誠に残念だが、その案は採用されなかった。
It is truly regrettable, but that proposal was not adopted.