howcome和why的区别：含义不同、用法不同、强调重点不同。howcome的含义为“为什么”、“怎么会”，常用于口语中，不在书面语中出现；why可作副词、名词和感叹词，含义为“为何、何必、哎呀、理由、说明”，可用于口语，也可用于书面语。
一、how come的含义及用法
how come意为为什么；怎么会…（那样）。例句有：
1、How come he hasn't been able to be as good this year?
为什么他今年表现不及往常呢？
2、How come you look so thin these days?
你最近瘦了，怎么闹的？
3、How come you, one of the family, are speaking like a stranger?
一家人怎么说起远话来了？
4、How did he come to break his leg?
他怎么把腿弄断的？
5、How did you come by that cheque?
你是怎么弄到那张支票的？
6、How will that come off, do you think?
那件事的结果将会如何，您想过没有？
二、why的含义及用法
why可作副词、感叹词和名词，意为为什么？;(用于问句)为什么，为何;(反问，表示不必)何必;(说明理由)为什么，…的原因；哎呀，呦，哟，嗨；原因;理由;说明;难解的问题。例句有：
1、Why were you late?
你为什么迟到？
2、Why get upset just because you got one bad grade?
何必因为一次成绩不好就想不开呢？
3、I know you did it─I just want to know why.
我知道这是你干的，我只是想知道为什么。
4、Why, it's easy─a child could do it!
嗨，这容易得很，连小孩子都干得了！
5、Why don't you look where you're going?...
走路怎么不看着点儿道呢？
6、There's a reason why women don't read this stuff; it's not funny...
女人不读这种东西是有原因的，它并不好笑。
