Perdón: is a noun, and you can actually use it as "I'm sorry", "sorry" but aslo as "forgiveness". Perdona: it means also "sorry" but it is a verb, so in a sentence it will work as a verb. In this case I'm asking you to forgive me in an informal way. The subject in a sencence with "perdona" is"tú". Perdone: the same as "perdona" but this time it is formal, it is the same verb but the subject change to"usted" (that is the formal way to the second person). Hope this will make sence to you :)

If you want to apologize to someone then you have these options: 1) Perdone: it's used in a formal way for people you don't know or aged persons. 2) Perdona: this is for informal situations usually when you know the person you're talking to or for young/middle-aged people. 3) Perdón: you can say it in both cases 1 & 2 or when talking about the nouns pardon/absolution. Notice I write from a Spaniard point of view ;)

Perdón: It is said pretty much as "excuse me" in English. You use this for example when you are in a meeting and your mobile phone rings and you have to pick it up. Then, you say: "perdón" as you leave to pick up the phone. Apart from that in Spanish is a noun and you could use it as "forgiveness". Perdona: It is word you would use when you want to apologize to someone. It is translated as "I am sorry". Moreover, "Perdón" and "Perdona" can be used in the same situations and can be translated both as "Excuse me". For example when you ask someone: Excuse me, would you let me that?, In Spanish: Perdón (o perdona), ¿me dejas eso? Perdona: Same as "Perdona" but in a polite way. You say this when you are whith people you want be as respectful as you can to. I hope I help you

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.