pronoun
you (polite, to male equal or superior)
Polite second-person pronoun used by men, typically in letters, to address a male equal or superior. Not used in casual speech.
貴兄にはますますご清栄のこととお喜び申し上げます。
I am delighted to hear of your continued good health and prosperity.
先日は貴兄よりご丁寧なお手紙をいただき、ありがとうございました。
Thank you for the kind letter I received from you the other day.