現(xiàn)在完成時(shí)
句型:have/has+過(guò)去分詞
現(xiàn)在完成時(shí)表示動(dòng)作發(fā)生在過(guò)去,但與現(xiàn)在有關(guān)系,即用一個(gè)發(fā)生在過(guò)去的動(dòng)作來(lái)說(shuō)明現(xiàn)在的情況。

過(guò)去完成時(shí)
句型:had+過(guò)去分詞
過(guò)去完成時(shí)表示在過(guò)去某一段時(shí)間或動(dòng)作以前已經(jīng)完成的動(dòng)作。強(qiáng)調(diào)過(guò)去的過(guò)去。

比較
現(xiàn)在完成時(shí)側(cè)重對(duì)現(xiàn)在產(chǎn)生的結(jié)果或造成的影響,與現(xiàn)在有關(guān);過(guò)去完成時(shí)則表示動(dòng)作發(fā)生在過(guò)去,強(qiáng)調(diào)過(guò)去的過(guò)去。與過(guò)去其他動(dòng)作比較時(shí)才會(huì)用到。

例句對(duì)比:
(1)
I have eaten lots of cakes so far. 到現(xiàn)在為止我吃了很多蛋糕了。
I had eaten lots of cakes till then. 在那之前我已經(jīng)吃了很多蛋糕了。

(2)
I have already finished reading the novel. 我已經(jīng)讀完了這本小說(shuō)。
I had finished reading the novel by nine o'clock last night.到昨晚9點(diǎn)鐘,我已經(jīng)讀完了這本小說(shuō)。

(3)
We have learned over two thousand English words. 我們已經(jīng)學(xué)了二千多個(gè)英語(yǔ)單詞。
We had learned over two thousand English words by the end of last term. 到上學(xué)期末我們已經(jīng)學(xué)了二千多個(gè)英語(yǔ)單詞。

(4)
The bus has already left. 車已經(jīng)開走了。
By the time I went outside, the bus had already left. 我到外面去的時(shí)候,車已經(jīng)開走了。

(5)
It has already stopped raining. 雨已經(jīng)停了。
When I woke up, it had already stopped raining.當(dāng)我醒來(lái)時(shí),雨已經(jīng)停了。