语法 | 现在完成时

现在完成时用来表示之前已发生或完成的动作或状态，其结果的确和现在有联系。

其构成：have (has) +过去分词。

I've already read this book.

我已经读过这本书了.

I've washed my clothes already．

我已经洗了衣服.

动作或状态发生在过去　但它的影响现在还存在；也可表示持续到现在的动作或状态。

I've lived here since 1990．

 = I've lived here since 13 years ago.

 = I've lived here for 13 years.

 = It is 13 years since I began to live here.

自从1990年以来我就住在这里.