It is +一段时间+since+从句 和 beforeIt is +一段时间+since(before)+从句 since 和before 有什么区别吗

问题描述:

It is +一段时间+since+从句 和 before
It is +一段时间+since(before)+从句
since 和before 有什么区别吗

it is 5 days since i left the hospital.之后 it is 5 days before i left the hospital.之前

since是在...之后,从..以后/以来
before 是在...之前
你说的那两个词都是在句中做连词
It is a long time before the building was accomplished.
这个建筑花了很长时间才建立起来
It has been a long time since Susan said that she want to give up smoking.
离Susan表示她想戒烟已经过了很久了

It is +一段时间+since...意思是“自.发生以来已经一段时间了”.如:it is three years since he died.(自)他去世以来已经三年了.It is +一段时间+before...意思是“过了一段时间...才发生”如:It is 3 years befor...

如果用before,谓语应该用过去时。而since一般用现在完成时。前者强调过去怎样,后者强调过去的一段时间多现在造成的影响。
before:在,,,之前
since:自从,,,