Discipline means training yourself or others to follow rules and maintain good habits, even when it's difficult. When you practice piano every day whether you feel like it or not, you're showing discipline. When a soccer player runs extra drills to improve their skills, that's discipline too.

The word has two main sides. First, it's the inner strength to do what you should do instead of what's easiest. A student with discipline finishes homework before playing video games. An artist with discipline keeps practicing even when progress feels slow. Second, discipline means the correction or consequences that help people learn to follow rules. When a teacher assigns detention for repeated tardiness, that's a form of discipline.

Discipline isn't about being rigid or joyless. It's about building the habits and self-control that let you achieve goals that matter to you. Olympic athletes have tremendous discipline, practicing for years to compete at the highest level. Musicians, scientists, and skilled craftspeople all rely on discipline to master their work.

The word can also mean a field of study or area of knowledge, like “the discipline of mathematics” or “the discipline of history.” Here it means an organized branch of learning with its own methods and standards.