An apology; the act of expressing remorse or regret (noun; can be used with 'suru' to mean 'to apologize').
彼はすぐに謝罪の言葉を述べた。
He immediately expressed words of apology.
会社は公式に謝罪した。
The company issued an official apology.
謝罪の手紙を送るつもりだ。
I plan to send a letter of apology.