useless

形容词 useless:

1. having no beneficial use or incapable of functioning usefully

1. It's useless to continue such a barren argument.
   继续这种无聊的争辩是无用的。
2. I had expended much time on the work but they told me it's useless.
   我花了很多时间在这件工作上，他们却告诉我说这是无用的。
3. It's useless to argue with them.
   同他们争论是没有用的。