In a manner based on or consisting of anecdotes rather than comprehensive data or scientific evidence.
From anecdotal (adjective form of anecdote) plus the adverbial suffix -ly. The adverb form allows speakers to qualify statements as being based on stories rather than facts.
You'll hear this word constantly in modern conversation—'anecdotally, I've noticed...' has become how people signal they're sharing a personal observation that might not apply universally, showing linguistic awareness of the evidence-versus-story divide.
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