If we think of someone other than their parents; Someone who khoioprom him and give him knowledge of the subjects that we tired by that he did not expect any compensation thing. One man who is not also "teacher."
If we imagine someone. Other than our parents. He's the one that delivers training and knowledge. That we tried, That he never expected any reward. Someone who is not the "master".
If we imagine someone besides our parents? Someone he's been training and give knowledge that tired to us. He never disappointed as any reward. That person is none other than "teacher"!