1. You don't have to call them every day, just to let them know you're not fighting
2. You don't have an anniversary--you just sort of "became" best friends.
3. When someone calls your girlfriend/boyfriend your "partner" it makes you think of marriage. When they call your best friend your partner, it's more like cops.
4. You never have to touch your best friend when it's hot outside, but you can stull huddle close when it's freezing.
5. Your parents usually like your best friend.
6. Your best friend doesn't care if you get fat, you're ugly, or if you get a bard haircut.