Meaning of “apology” - Learner’s Dictionary

apology

noun [ C, U ] us uk /əˈpɒlədʒi/

B1 something you say or write to say that you are sorry about something you have done:

I have an apology / to make to you - I opened your letter by mistake.
a letter of apology

(Definition of “apology” from the Cambridge Learner’s Dictionary © Cambridge University Press)