In a skillful, quick, and neat way; with smooth and precise movements or actions.
From 'deft' plus the adverbial suffix '-ly,' which comes from Old English -lice. The adverb form allows the adjective quality to modify verbs and other adjectives.
Adding '-ly' to make adverbs is so common we barely notice it, but it's one of English's most productive word-building tools—you can almost always turn an adjective into an adverb this way.
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