跟我们一起吃午餐吧。

[mass noun]do join us for lunch.

他请她吃了顿高档午餐。

He treated her to a slap-up lunch.

他为20个人供应了午餐。

He catered a lunch for 20 people.

一份牛皮纸袋包的自带午餐。

[as modifier]a brown bag lunch.

没有免费午餐之类的东西。

There is no such thing as a free lunch.