Elder -
An assassin elder is a retired man, which begins to train Student assassins, and passes his knowledge onto the younger, newer assassins.
Dux -
A true master in everything assassin. They will have information and are heavily knowledgeable on most things. They are never normally young.
Master -
To teach the apprenticed assassins, they follow to strive to become a Dux. However, many just remain masters, with high respect for any Dux, from any Brotherhood.
Apprentice -
A minor assassin, will have had a few kills here and there, but they would have been small compared to Master, Dux and Elder.
Student -
A new one, a one to learn from a master.