情态动词would的用法详解
Would的用法有很多
在Oxford Learner’s Dictionaries里查找would，多达14个解释意义。要熟练、正确地掌握这些解释词条的确要花一番功夫。但是，对于这样的单词一旦掌握，对提升语言能力是非常明显的——以前看不懂的，或者总感觉稀里糊涂的地方，一下子豁然开朗了。
它在某些语义下，能和could互换的，影响不大。可能只有英语母语者能体会的细微差别。比如：
Would you open the door for me, please?Could you open the door for me, please?
Would可以表示强调有主观性的意思，相对应的could表示多一些客观的可能性。这点在写作时留意，就能在情态动词之间选择合适的了。
最经典就是Even if I could, I wouldn’t!
一类就是作为will的过去式
站在过去的时间点看将来，例如：
What happen if there were pests?如果有害虫怎么办？应该填would。
What happen if there are pests? 这里就应该填will。
还有在间接转述别人话时，他们正好表达了将来时，那么就得用would，例如：
He said he would be here at eight o'clock (= His words were: ‘I will be there at eight o'clock.’).She asked if I would help.They told me that they probably wouldn't come.
但是，有时候would由“将来、将要”引申为，“可能，接着……，因此”的含义，但是不是语法层面的，而是语义上，例如：
She'd look better with shorter hair.If you went to see him, he would be delighted.Hurry up! It would be a shame to miss the beginning of the play.She'd be a fool to accept it (= if she accepted).
但是加红色字体这句，我不太确定是说“你如果当时去看他，他会非常开心的。”，表示一种对过去某事的预测，跟“If you go to see him, he will be delighted.”这一句含义有什么区别。期待有人能给权威的解答。
还有一个用法就是——虚拟语气
would have done something used for describing a possible action or event that did not in fact happen, because something else did not happen first
例如：
If I had seen the advertisement in time, I would have applied for the job.They would never have met if she hadn't gone to Emma's party.
