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polite; courteous; civil
careful; close; thorough; conscientious
overly courteous; overly careful; overly thorough
彼は御丁寧に遅刻の理由まで述べた。
He went so far as to explain his reason for being late.
御丁寧なお便りをありがとうございました。
Thank you for your very courteous letter.
わざわざ謝罪文に御丁寧に手書きで署名まで添えてあった。
They even went out of their way to add a handwritten signature to the apology letter.