To say sorry for a mistake or a problem that was caused.
“We sincerely apologize for the delay in processing your order.”
“I would like to apologize for the confusion caused by our earlier email.”
This word almost always signals a negative or apologetic tone, often in a response letter addressing a complaint. Recognizing it quickly helps with tone questions, since it shows the writer is acknowledging fault rather than simply giving information.
Synonyms: express regret, say sorry, ask forgiveness