過(guò)去分詞。had done用于過(guò)去完成時(shí)，過(guò)去完成時(shí)即“過(guò)去的過(guò)去”，過(guò)去已經(jīng)發(fā)生過(guò)的事。例句：By the end of last term，we had learned 5000 new words.到上學(xué)期末，我們已經(jīng)學(xué)了5000個(gè)新詞。

had后面的動(dòng)詞的形式

had后面用動(dòng)詞過(guò)去分詞形式，即had done。

had done是過(guò)去完成時(shí)。表示動(dòng)作發(fā)生在過(guò)去的過(guò)去。通常句中有過(guò)去時(shí)間狀語(yǔ)作參照。

例句：I had finished my homework before my father came back.

在我父親回來(lái)之前，我已經(jīng)完成了家庭作業(yè)。

had done句型的例句

They had never seen so many of the locusts before.

（他們以前從未見(jiàn)過(guò)如此多的蝗蟲(chóng)）

I had reached the station before six o'clock.

（六點(diǎn)之前我已到達(dá)車(chē)站。）

Fortunately, the population had left the village before the volcano erupted.

（幸運(yùn)的是，火山噴發(fā)前人們已離開(kāi)了村莊。）