yet,however,while都有然而的意思,三者有什么区别,举例子.

yet(用于疑问句和否定句)
还,尚,仍
He has not come yet.
他还没有来.
She is yet a child.
她还是个孩子.
He was poor,yet happy.
他很穷,可是很快乐.
The driver's not yet conscious after the accident.
驾驶员在出事后,还没有苏醒过来.
The doctors have not yet decided how the woman died.
医生们尚未确定这位妇女的死因.
whlie只能和延续性动词连用(常用于过去进行时)
n.一会儿,时间
conj.当...的时候,虽然
vt.消磨
prep.直到
however
然而,但是
adv.无论如何,可是,仍然,究竟
conj.不管用何种方法,然而,可是