'Decorum' is Latin for 'what is fitting' — from 'decere' (to be proper), root of 'decent' and 'dignity.'
Definition
Behavior that is considered correct, tasteful, or socially acceptable.
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Latin1560swell-attested
From Latin 'decorum,' the neuter singular of the adjective 'decorus' (fitting, proper, seemly, beautiful), used as a noun meaning 'that which is fitting' or 'propriety of behaviour.' 'Decorus' derives from 'decor' (beauty, grace, elegance, that which adorns), from 'decere' (to be fitting, to be becoming, to be suitable), from PIE *dek- (to take, to accept — in the extended sense of what is accepted as appropriate or excellent). The same PIE rootproduced
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TheLatin 'decēre' also produced 'decent,' 'decorate,' and 'dignity.' Propriety was, for the Romans, a form of beauty.
and vice versa. It widened to general behavioural propriety in the 17th and 18th centuries. For the Romans, decorum was inseparable from aesthetics: to be fitting was to be beautiful. Key roots: deco (Latin: "From Latin 'decōrum' meaning 'that which").