Preceptor is a noun that refers to a tutor or instructor. 

The Latin word praeceptor (pry CEP tor) means ‘teacher’ or ‘instructor.’ Joining English in the Late Middle English period, our word of the day is a synonym of teacher but is more likely to be used in a formal, academic context like medical school. For example:

The wisest advice I’ve ever gotten from a teacher came to me in medical school where my preceptor recommended I spend some time to touch up my Latin. After all, I’d never become a doctor if I couldn’t pronounce words like cranium, femur or dorsalis pedis.