Discipline is both a noun and a verb. It is the act of training someone physically or mentally, either someone else or yourself. The term can also be used to describe the action of punishment. In the case of The Brotherhood, discipline is the vehicle to help young men who arrive at better versions of themselves. It is beyond grammatical rules — it is the concept of purpose, directly administered.
In the case of young Apprentice Monroe, the time for his discipline had come. He had already been with, and vetted by, Masters Figata and Kamp. He had learned much about the pleasure of men, and his expected role in providing it. What he had not learned yet, but will, is that pain can be a pleasure, too. It can lead to something larger, something grander than oneself. And a grander and larger presence than any Apprentice Monroe had met before waited for him in a darkened room. He felt a chill run through him at the sight of this imposing figure. This powerful man, carved by time and strength, with the eyes of a hawk and the kind of smile that made one feel small, was Grandmaster Legrand.