Propriety

noun: the quality of behaving in a proper manner, obeying rules and customs

1. The quality of being proper; appropriateness.
2. Conformity to prevailing customs and usages.
3. proprieties The usages and customs of polite society.

The aristocracy maintained a high level of propriety, adhering to even the most minor social rules

Synonyms: appropriateness, decency, decorum, modesty