出典:Wiktionary
From Middle English helpful; equivalent to help + -ful.
helpful (comparative more helpful, superlative most helpful)
to be helpful
a helpful person
to help a person out of a difficulty
a helper
to be a help to one―help to do something―tend to do something―have a share in doing something―be instrumental in doing something―contribute to some result―conduce to some state―go far towards the result―do much towards the result―make for some state
to help a person accomplish something
a person who helps accomplish a task