表示過(guò)去某段時(shí)間正在進(jìn)行的動(dòng)作.
Shirley was writing a book about China last year but I don't know whether she has finished it.舍利去年在寫(xiě)一本有關(guān)中國(guó)的書(shū),但我不知道他是否完成.
They were building a dam last winter.去年冬天他們?cè)诮ù髩?
一般過(guò)去時(shí)與過(guò)去進(jìn)行時(shí)用法比較
一般過(guò)去時(shí)表示在過(guò)去某個(gè)時(shí)間發(fā)生的動(dòng)作或存在的狀態(tài)（強(qiáng)調(diào)一次性動(dòng)作）；而過(guò)去進(jìn)行時(shí)則表示在過(guò)去某一時(shí)刻或某段時(shí)間正在進(jìn)行的動(dòng)作（強(qiáng)調(diào)反復(fù)的動(dòng)作）.
Mary wrote a letter to her friend last night.瑪麗昨晚給她的朋友寫(xiě)了封信.（寫(xiě)完了）
Mary was writing a letter to her friend last night.瑪麗昨晚一直在給她的朋友寫(xiě)信.（不一定寫(xiě)完）
We built a bridge last winter.去年冬天我們修了一座橋.（建成了）
We were building a bridge last winter.去年冬于我們?cè)谛抟蛔鶚?（一直在修,不涉及結(jié)果）