Friendship definition

I've been trying to define friendship lately...I keep asking myself..
What is the definition of best friends?
What is definition of bad friends?

I have browsed the dictionary.. and it doesn't help much this time.
so I will try to define it myself.

For me, friendship is like a relationship.. you need to find a person who can grow up at the same phase with you.
Friendship should be a benefit for both parties, where you resonate things without saying  too many words, where one doesn't need to keep telling other parties to do this and that continuously, where you can create comforts for being with each other.
Friendship should involve trust.. when lies involved, trust broken, then the friendship is gone.

There are times, when I acuse myself as a not so good friend when my friend probably need me badly- I can't stand when my friends keep whining without doing the acts and I can't stand the immature talks involving too much feeling. 
I have been trying to keep reminding myself that friendship should be unconditional, that I should be there in good and bad times. But, then I think, my style of friendship is a different one, I am tough and logic and will not involve pity in a friendship. 

OH, I know this isn't a perfect definition of friendship.
The good thing about my imperfect writings.. everyone can define their own definition of friendship :) 
here is some inspiration for you and me to define friendship : 

Choose your friend wisely fellas!