1）過去進行時和一般過去時的基本差別是，過去進行時表示一個正在進行的動作，而一般過去時表示一個業已完成的動作。試比較下面的句子：
She was knitting a sweater for Tom. 她在給湯姆織一件毛衣。
She knitted a sweater for Tom. 她給湯姆織了一件毛衣。
He was doing his homework in the afternoon. 下午他在做作業。
He did his homework in the afternoon. 下午他把作業做完了。
I was writing an essay. 我在寫一篇論文。（可能還沒寫完）
I wrote an essay yesterday. 我昨天寫了一篇論文。（已寫完）
They were building a skyscraper. 他們在建一座摩天大樓。（在修建）
They built a skyscraper. 他們蓋了一座摩天大樓。（已蓋好）
2）有些動詞本身并不表示動作完成，如 rain, snow, cough, wear, feel, wait, stay, work等，這時用兩種時態意思上差別不大：
It snowed all night. 下了一整夜的雪。
It was snowing all night.
She wore a blue coat. 她穿著一件藍外套。
She was wearing a blue coat.
He felt a bit uneasy. 他感到有點不自在。
He was feeling a bit uneasy.
We stayed in a hotel. 我們住在旅館里。
We were staying in a hotel.
3）用進行時態有時有感情色彩，特別是帶有always, forever, constantly這類狀語時，如：
He was always ringing up. 他總是給我打電話。（厭煩）
She was always working. 她總是不停地干活。（贊揚）
The old lady was forever grumbling. 這老太太老是嘀嘀咕咕。（厭煩）
He was constantly changing his mind. 他總是改變主意。（不以為然）
4）有時用進行時表示現在的想法，可以顯得客氣一點，如：
I was wondering whether you could give me some advice. 不知你能否幫我出點主意。
I was thinking maybe he could go by taxi. 我在想或許他可以坐的士去。
I was hoping you could reconsider our proposal. 我希望你能再考慮一下我們的建議。
表示過去某時預計要發生的情況的用法
有些結構可以表示過去某時打算要做的事或預計要發生的事，如：
1）過去進行時（僅限于come, go, leave這類動詞）：
He was busy packing, for he was leaving that night. 他忙著收拾行李，因為那晚他就要走了。
Mr. Brown was coming to dinner. 布郎先生要來吃晚飯。
She told me she was going to Boston. 她告訴我她要去波士頓。
We were very excited as we were flying to Europe the next morning. 我們很激動， 因為第二天早晨我們就要飛往歐洲了。
2) was going to:
She said she was going to come early. 她說她一早就來。
Judy was going to meet me, but she was ill and couldn’t come. 朱迪本來是要來和我們會面的，但她生病了沒能來。
When I arrived, the train was just going to start. 我到車站時火車正要出發。
3) be about to (表示“就要”、“即將”發生某事)：
He was about to go out when the phone rang. 他正要出去時電話響了。
I was just about to explain when she interrupted me. 我正要解釋，她打斷了我的話。
It was seven o’clock. The show was about to start. 七點鐘了，演出即將開始。
4) be due to（表示“定于”）：
He was due to speak that night. 他定于那天晚上發言。
Mary was due to leave at 2 o’clock. 馬麗定于兩點出發。
The conference was due to start in 2 weeks’ time. 會議定于兩周后開始。
She was due to graduate in the coming summer. 她將于這個夏天畢業。
表示過去某時預計要發生的情況的用法
有些結構可以表示過去某時打算要做的事或預計要發生的事，如：
1）過去進行時（僅限于come, go, leave這類動詞）：
He was busy packing, for he was leaving that night. 他忙著收拾行李，因為那晚他就要走了。
Mr. Brown was coming to dinner. 布郎先生要來吃晚飯。
She told me she was going to Boston. 她告訴我她要去波士頓。
We were very excited as we were flying to Europe the next morning. 我們很激動， 因為第二天早晨我們就要飛往歐洲了。
2) was going to:
She said she was going to come early. 她說她一早就來。
Judy was going to meet me, but she was ill and couldn’t come. 朱迪本來是要來和我們會面的，但她生病了沒能來。
When I arrived, the train was just going to start. 我到車站時火車正要出發。
3) be about to (表示“就要”、“即將”發生某事)：
He was about to go out when the phone rang. 他正要出去時電話響了。
I was just about to explain when she interrupted me. 我正要解釋，她打斷了我的話。
It was seven o’clock. The show was about to start. 七點鐘了，演出即將開始。
4) be due to（表示“定于”）：
He was due to speak that night. 他定于那天晚上發言。
Mary was due to leave at 2 o’clock. 馬麗定于兩點出發。
The conference was due to start in 2 weeks’ time. 會議定于兩周后開始。
She was due to graduate in the coming summer. 她將于這個夏天畢業。
