Yo, Profz!
Choose an appropriate greeting. “Hi/Hello Professor [Blank]” is always appropriate. Substitute “Dear” and you’ve ended up writing a letter; leave out “Hi” and your tone is too brusque.
For all those of you who are still entrenched in skool, here is a guide on how to email your professor, which I think can also be applied to lecturers, teachers, tuiton teachers, tennis coaches and your guitar instructor.
Cowboy Caleb recommends 

