In a way that shows authority, confidence, and the power to make decisions; speaking or acting with definitive command or expertise.
From 'authoritative' (from 'authority' + '-ative' meaning 'tending to') plus '-ly' (Old English suffix for adverbs). The term describes the manner in which authority is exercised or expressed.
People often speak 'authoritatively' about things they barely understand—it's why confident wrongness can be so persuasive, and why science communication has to work hard to convey real expertise without sounding too sure about uncertain things.
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