but for表示要不是的意思，相当于if it were not for, if it had not been for。它常用于虚拟语气。for 是介词，其后只能接名词（词组）。
例如：But for your help and guidance, I should fail.要不是你的帮助与指导，我早就失败了。
but that 表示除……以外，除非等意思，相当于except that; 也可以表示要不是的意思。but that后接从句。例如：We ask nothing from you but that you should give a clear statement of the facts.我们什么也不要你的，就是要你把实情清楚地交代出来。
He would have helped us but that he was short of money at that time.要不是他当时没有钱，他就帮助我们了。
It will go hard but that we shall bring more land under cultivation.除非我们扩大耕地面积，否则事情就不好办。下载本文
