Behavior or conduct that is appropriate, proper, and respectable; propriety or decorum.
From Latin decentia, from decere (to be fitting or suitable), related to the word 'decent.' Entered English in the 16th century meaning proper conduct or social appropriateness.
Decence was a huge deal in formal societies—you could be punished socially for breaking rules of decence that aren't even written down, which is why people got so anxious about etiquette in Victorian times.
Complete word intelligence in one call. Free tier — 50 lookups/day.