1.
sincerity; faithfulness; integrity
A heartfelt, honest attitude; loyalty and trustworthiness in one's words and actions. A core virtue in traditional Japanese ethics, often associated with bushidō and Confucian values.
2.
truth; reality; fact
What is actually the case; truth as opposed to falsehood. Somewhat literary or formal; everyday speech uses 本当 instead.
An older native Japanese word that has taken on a somewhat formal or literary tone in modern usage. Also a very common given name (especially masculine).
ADVERBIAL USE — 誠に:
The most frequent modern usage is as the adverb 誠に (truly, sincerely, indeed), heard in polite business expressions:
- 誠にありがとうございます: thank you very much (sincerely)
- 誠に申し訳ありません: I am truly sorry
- 誠に恐縮ですが: I am truly sorry to trouble you