我已经吃过晚饭了.I have already had dinner.对吗?

对的。already是个副词，去掉后不影响句子，变成I have had dinner.很明显是现在完成时，所以是对的。

I already have dinner.才对 ,例如You already have all you need.这是在课本上找的

回答的什么玩意，别误导人！我的绝对对！I had a dinner！呵呵，希望采纳！

I have already had dinner.