apology · noun C or U /əˈpɒl.ə.dʒi/
apology
B1 something you say or write to say that you are sorry about something you have done
Dictionary examples:
I have an apology to make to you - I'm afraid I opened your letter by mistake.
I owe you an apology, Chris.
"Was he at all sorry for what he'd done?" "Oh he was full of apologies."
Learner example:
Hi Zita, Please accept my apology for this belated letter which you're holding in your hands. (Preliminary English Test; B1; Hungarian)