Teacher are persons who teach.
There are teachers for mathemathics, and there are teachers for grammar, and there are teachers for life.
The teachers, who teach things for life are the most worthfull ones. They teach you that life is bullshit, everybody is a gambler and either hit or get beaten.
You have to be very thankfull to your teachers for life.
I am thankfull to my big hero, my teacher for life.