In a useful manner; in a way that achieves something(adverb)
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Use "usefully" in a sentence
"Those who enjoy the show inhabit that world, and presumably wish to continue living there, and thus the mockery of its manifestations and assumptions remain usefully "corrective," reminding them that it can all be quite ridiculous."
"Long empty streets, red, orange, golden leaves, sunlight and moonlight almost become actors in usefully letting the Halloween (the holiday) feel be so present."
"The frieze, too, affords a means of contrast in line to the line system of the field of the wall, its horizontal expression usefully opposing the verticals or diagonals of the wall pattern below."