perdon vs. lo siento
Perdon, in usage, is more like excuse me.
When you need to cross in front of someone shopping at the grocery store, you say Perdon.
If in the process, you knock over their cart, you say lo siento.
If someone told you that their mother had just died or some other awful news you would say: Lo siento mucho meaning you feel very sorry. Perdone is just an excuse me.
perdon--pardon or forgiveness vs. lo siento--- I'm sorry. Both are words for feeling sorry or asking for forgiveness. I hope this helps.
Perdón is like "Pardon me." If you say "Lo siento," hopefully the response will be "de nada" (it's nothing) or "don't worry about it." Lo siento implies that whatever happened is an unfortunate accident. Apologizing for a serious mistake or purposeful action is "Pido disculpas," -It is my fault