Friends or Aquaintances?

I look back from my elementary years and friends i've made eversince. Surely some remain outstanding and maybe they can be called friends or can they? what is a friend? How many friends can one person have? one? two...ten? I always wonder. I have several friends and they are all different, the only common thing about them is that they are my friends. Sometimes it gets really confusing as i want to rate some as more friends than others but only to realise that i no longer know that much about them and them about me. Hm! Can they be now referred to as acquaintances? How do i refer to someone i have known for over twenty years and have kept consistent communication with as just an acquaintance? I have their mobile number, their home number...i occationally visit their work place and the colleaques know that i am their visitor. We occationally share a tear over the universes negative impact on us? But are they a friend? i sometimes forget what grade their children are? They dont even know who i am currently dating?....Hm! How does one rate their best friend? Can one really have only one best friend?