Permiso means: Excuse me, may I come in. It is used when you come to a place or when you try to get through a crowd of people. It also means excuse me when you try to reach something. For example: “permiso, puedo pasar”, “permiso, por favor” “permiso, voy a agarrar este libro” In some countries you can say “con permiso” Disculpe, Disculpa, perdón mean: I'm sorry. It depends on the context. It’s very common when you need to ask for something, or to say “sorry to bother you” For example: "Disculpa, ¿puedes decirme la hora?" “Disculpe ¿puede prestarme su lápiz? Perdón is used when you are very sorry about a mistake, this is the perfect word to apologize, it is more sentimental when you feel very bad for something. “perdón, cometí un error”, “perdón no volverá a ocurrir”. “Perdoname por haberte fallado” “perdóname” The word “perdon” can be used to ask for something and it is very polite: "Perdón, ¿puede decirme la hora?"