Certainly or definitely, in a way that shows confidence that something is definitely true.
From 'assured' (made certain or confident) plus the adverb suffix '-ly.' 'Assured' comes from Old French 'asseurer' (to assure), from Latin 'ad-' and 'securare' (to secure).
The word has an old-fashioned, formal sound that's disappeared from everyday speech—people now say 'definitely' or 'for sure,' but 'assuredly' still carries a weight and confidence that modern words have lost.
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