dignified
Calm, respectful, and serious in a way that earns respect.
Dignified describes someone who carries themselves with calm self-respect and seriousness, or something done in a way that shows respect and proper behavior. A dignified person doesn't need to brag or show off: their bearing and conduct naturally command respect.
Think of a judge entering a courtroom with steady steps and a composed expression, or a principal addressing students about a serious matter with calm authority. They're being dignified. When you accept losing a close game without complaining or making excuses, you're showing dignified behavior. When you speak up for yourself without yelling or name-calling, that's dignified too.
The word often describes how people handle difficult situations. Someone who faces disappointment with grace, or receives criticism without getting defensive or mean, acts with dignity. A dignified response to rudeness might be simply walking away rather than arguing.
Places and events can also be dignified: a simple but respectful funeral service, a graduation ceremony conducted with proper seriousness, or even a quiet, well-kept library. The opposite would be chaotic, silly, or disrespectful.
Being dignified doesn't mean being stiff or unfriendly. You can laugh, play, and have fun while still treating yourself and others with respect when it matters.