過去分詞。had done用于過去完成時，過去完成時即“過去的過去”，過去已經(jīng)發(fā)生過的事。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個新詞。

had后面的動詞的形式

had后面用動詞過去分詞形式，即had done。

had done是過去完成時。表示動作發(fā)生在過去的過去。通常句中有過去時間狀語作參照。

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

在我父親回來之前，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.

（他們以前從未見過如此多的蝗蟲）

I had reached the station before six o'clock.

（六點(diǎn)之前我已到達(dá)車站。）

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

（幸運(yùn)的是，火山噴發(fā)前人們已離開了村莊。）