This is the 1059th most frequent Japanese word.
師
"師" means "teacher," "master," or "mentor."
In this sentence, '師' is used in '医師' (ishi), which means a doctor—indicating a person practicing medicine professionally.
彼の父は医師です。
His father is a doctor.
Here, '師' refers to a mentor or a teacher, someone who provides guidance in life matters.
私は彼を人生の師と考えています。
I consider him as a mentor in life.
In this context, '師' appears as part of '師範' (shihan), referring to a master instructor, particularly in martial arts or specific skilled disciplines.