noun
thank-you letter; letter of apology
A formal written letter expressing gratitude or apology. The specific meaning depends on context; often used in official or business settings.
お世話になった方に謝状を送った。
I sent a thank-you letter to the person who helped me.
不手際のお詫びとして謝状を提出した。
I submitted a letter of apology for the mishandling.