noun
A somewhat formal or literary noun expressing utmost sincerity and wholehearted devotion. Often used in serious contexts such as moral philosophy, speeches, or written expressions of commitment.
彼の至誠のこもった言葉に、皆が心を打たれた。
Everyone was moved by his words filled with utmost sincerity.
至誠をもって事に当たれば、必ず道は開
If you approach matters with complete sincerity, a path will surely open.
A Sino-Japanese compound of 至 (utmost) and 誠 (sincerity), literally meaning 'utmost sincerity'. The exact historical derivation is uncertain, but the word has been used in classical Chinese and Japanese texts to denote the highest degree of sincerity and devotion.