1、用于过去将来时，如：
He said he would come. 他说他要来。
He said that he would be forty on his next birthday. 他说到下次生日他就四十岁了。
2、用来表示愿意/ 偏要/肯这种个人意愿，如：
He would eat nothing. 他不肯吃东西; 他什么也不愿吃。
I told him not to go, but he would not listen. 我叫他别去, 可他偏不听。
He would go in spite of our warnings. 他不听我们的劝告, 执意要去。
3、表示过去的习惯动作，如：
He would sit for hours doing nothing. 过去他常常坐几个钟头，什么事也不做。
He would come to see us on Sundays. 星期天他过去经常来看望我们。
4、表示可能性或不确定性，如：
I would be about ten when my brother left home. 我哥哥离开家时, 我大概十岁左右。
It would seem to be getting warmer. 天气似乎变得更暖和了
5、用于虚拟语气，
1）表示假设，如：
I could do so if I would. 要是我愿意, 我能够这样做(但我不愿意)。
If you would do this for me, I should be grateful indeed. 若是你愿意为我做这件事, 我将万分感激 。
They would be killed if the car went over the cliff. 如果汽车翻在悬崖下, 他们就会丧命。
They would have been killed if the car had gone over the cliff. 如果汽车当时翻到悬崖下, 他们早就丧命了。
2）表示请求或个人想法、看法，使语气更婉转，如：,
Would you kindly show me the way to the station? 劳驾, 请问到车站的路怎么走?
I would like to speak a few words. 我想讲几句话。
Would you go with me? 你愿意和我一起去吗?
3）表示但愿、要是...该多好
Would that I were young again. 我若能再年青些该多好啊! (would 前常省略主语 I)
We wish that he would come again. 我们但愿他会再来。
I would rather you came on Sunday. 我倒是希望你星期天来 。