passion is enthusiasm with more emotion.

They slightly differ in meaning and are in some cases interchangeable. Enthusiasm is usually linked to an interest (e.g. in photography, in languages, etc.) Passion can also apply to an interest (with a stronger meaning), but it also applies to love and sexual relationships, lifelong commitments (e.g. a profession which you are willing to take up for life), both of which you should not use the word 'enthusiasm'.

I'm not a native so I can't say for sure, but for me passion is like a strong desire to do something, in good meaning. It is used in advertising, for example. Enthusiasm from the other hand is less then passion, like enthusiast photographer, not a proffessional one. I prefer to use passion when you're talking about the things that you really love and do and to use enthusiasm for things that just interest you but you often don't have enough time to do them.

Thanks for giving me helpful answers. I chose the most simple answer. I appreciate three awesome people.