as yet

副词 as yet:

1. used in negative statement to describe a situation that has existed up to this point or up to the present time
   同义词：so far, thus far, up to now, hitherto, heretofore, yet, til now, until now

1. The side-effects of the drug are as yet unknown (toscientists).
   这种药的副作用(科学家)尚未发现。
2. As yet we haven't heard from him.
   我们到现在还没有收到他的信。
3. We are as yet unable to say when the train will arrive.
   我们还说不上火车什么时候到达。
4. We should be responsible for the generation as yet unborn.
   我们应该对下一代负责。