Definitions of discipline:

• noun:   training to improve strength or self-control
• noun:   the act of punishing

  Example: "The offenders deserved the harsh discipline they received"

• noun:   the trait of being well behaved

  Example: "He insisted on discipline among the troops"

• noun:   a system of rules of conduct or method of practice

  Example: "He quickly learned the discipline of prison routine or for such a plan to work requires discipline"

• noun:   a branch of knowledge

  Example: "In what discipline is his doctorate?"

• verb:   punish in order to gain control or enforce obedience

  Example: "The teacher disciplined the pupils rather frequently"

• verb:   train by instruction and practice; especially to teach self-control

  Example: "Parents must discipline their children"