If和While有什么区别？

if 连接词 conj.
1.(表示条件)如果 He will come if you invite him.
2.(表示虚拟)假如,要是 If I were you, I would never do that.
3.(表示让步)即使 We'll go even if it rains.
4.是否 I wonder if she is ill.
5.(表示因果关系)每一次...的时候(总是会) If I feel any doubt, I inquire.

while 连接词 conj.
1.当...的时候,和...同时
She listened closely while he read the letter.
I'll take care of your children while you are away.
We must strike while the iron is hot. 趁热打铁。
2.而,然而 I like tea while she likes coffee.
3.虽然,尽管 While I like the color of the hat, I do not like its shape.
4.只要

if 和while 都可以引导表语从句。但if不能引导主语从句，只有while可以引导。

If表示如果，一般是用在条件状语从句中的。
很多时候都用于虚拟语气，如：If I were you这种句式里的。
while 一般表示当什么什么时候，后面的动词是ing形式的
另外最常用的意思是表示而的意思，Kate likes reading while Lily likes going skating.

1，在表示during the whole time that(长达……之久)或while(只要)的含义时,往往用as long as。例如：As long as there is life there is hope. 留得生命在,不怕没希望.
2，在表示on condition that, provided that或if(只要,如果)的含义时,用as long as或so long as的情况均很常见。例：I'll accept any job as / so long as I don't have to get up early. 只要不必早起,任何工作我都可以接受.
3，在表示since, considering that(既然,因为)的含义时,多用as long as。例：As long as you are going, I'll go too. 既然你要去,那么我也去.