The noun denoting the teacher is called Ablation or apādāna , in relation to the action signifying formal teaching.,
The word आख्याता means teacher, and उपयोग means acquiring knowledge in the regular way. Thus उपाध्यायादधीते or आगमयति he learns from the preceptor.
Why do we say 'when meaning to learn'? Observe नटस्य शृणोति he hears the player.,