“Saying sorry won't make you smaller”.
I'm not sure whether my question is reasonable or not but I was discussing this question with my friends, and got some points by them. We, actually, faced some challenges while deciding what PART OF SPEECH the word SORRY is in the given sentence!
Some of them called it as a NOUN and some of them called it as an ADJECTIVE.
I myself looked it up in different dictionaries, got answers as SORRY isn't used as a noun but an adjective.