im sorry = lo siento o perdon

It's said "lo siento" or "perdón" depending on the context. If you stumble upon anyone or step on his/her foot, you can either say "lo siento" or "perdón". But if when you're sharing out a birth cake it runs out and have to tell everybody, you say "lo siento, se acabó el pastel". If your friend's dad has just died and you want to show him/her your condolences, you must say "lo siento". Don't say "perdón" unless you want to let your friend know you've killed him. If someone grabs your handbag, you can say "perdona, pero esto es mío". Use "perdón" or "lo siento" to show your apologies when it is your fault. Use "perdón" or "perdona" to ask for a further explanation. Use "lo siento" to show your apologies or condolence when it's not your fault.