Decorous (adjective)

Behaving or conducting oneself in a proper, respectable, and polite manner; characterized by good taste and propriety; well-mannered.

Origin:

From the latin word "decorus" meaning "fitting" or "appropriate".

Examples:

1. She always conducts herself in a decorous manner.
2. He was decorous in his behavior.
3. The meeting was decorous, with no disruptions.
4. The party was decorous, with no loud music or loud talking.
5. The funeral was a decorous affair, with everyone dressed in black.