He performed the task rather usefully! ( He did it well because he was skilled) The word useful is an adjective. Usefully is an adverb. The adjective can be converted to a noun by adding ness to it - usefulness which is used more commonly than the adverb.
literary
ther is no such word as "usefully" that would be terrible grammar, try "useful" that way you could write a sentence for example:: " it is useful to use a dictionary when writing a letter".
Usefully - meaning the act of being useful.Usefully, he had left driving directions and his cell phone number, just in case they were to get lost.This text book is usefully short; it makes it so easy to digest.
From Wikipedia:"An aquiferis a wet underground layer of water-bearing permeable rock or unconsolidated materials (gravel, sand, or silt) from which groundwater can be usefully extracted using a water well."
I am not writing a sentence using that word.
I can give you a sentence using the word galaxy.
a sentence using the word endotracheal
This is a sentence using the word aviator.
I am saying a sentence using the word collagen.
This is a sentence using the word monomer. :P
this is a sentence using the word armchair.
your saving planets energ and using it usefully