A hammer is useful when putting up a shelf.
Studying is useful if you want to get a good grade on a test.
You just did, didn't you? What if you just write a useful sentence?
The internet can be useful and harmful.
Shrewdness is useful in negotiating a business transaction.
A portable computer is very useful.
Have you read the transcript? It was very useful.
The inventor invented lots of useful things
I hate transform boundaries!!
My wristwatch has an altimeter, which as a backpacker, I find very useful.
I can give you several sentences.Learning how to use words properly is useful.You should make yourself useful and help your aunt sweep the floor.Speaking English is a useful skill.
The detective gained useful information by following the trajectory of the bullet.
stylebook
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".