没用

nǐ zhēn méi yòng lián qù shāng diàn mǎi dōng xi dōu néng mí lù

你真没用！连去商店买东西都能迷路！

You're absolutely useless. Can't you even go to the shops without getting lost!

nà zhī bǐ méi yòng le

那支笔没用了。

That pen is useless.

zhè shì bǎ méi yòng de xiǎo dāo dāo bà r huài le

这是把没用的小刀，刀把儿坏了。

This is a useless knife. The handle has broken.