El perdón, it is the only word you can use as sustantive.
Perdone, pero usted esta equivocado! (formal)
Perdona, María pero te equivocas, no fui yo el que cogio las llaves. ( sorry marria, but you are wrong it was not me who too the keys. (as a way of saying, sorry, but not I am sorry) I am sorry is Lo siento.
Perdón, Señor, ¿Dónde quedan los baños? But once again, I don't use much perdon, we use more in colombia, Disculpe. Perdón it is like a book thing.