noun.control gained by enforcing obedience or order

• struggled to maintain discipline in the classroom
• The troops were praised for their dedication and discipline.

noun.behavior in accordance with rules: orderly conduct

• lacked the discipline to practice regularly
• was responsible for meting out discipline

noun.self-control

• … keep the discipline of putting money toward your savings regularly.
• Practicing running at this marathon pace … will be good discipline.

verb.to punish or penalize as a means of enforcing obedience and perfecting moral character

• debates about the proper way to discipline a child
• was disciplined for misbehaving in class

verb.to train or develop by instruction and exercise especially in self-control

• a player repeatedly disciplined by the league
• I'm trying to discipline myself to exercise each morning.

verb.to bring (a group) under control

• discipline troops
• Serious writers discipline and refine their writing styles.