Task
Use, Duty, Service, Business, Purpose
noun, suffix
The kanji and the word are exactly the same. That means they share meanings as well.
よう
This one uses the on'yomi reading, which you've learned from the kanji already!
なにも用がない。
I have nothing to do.
なにかご用ですか？
Do you need me for something?
用もないのにでんわしてくんじゃねーよ。
Don’t call me unless you have a reason.