as yet

Từ điển WordNet v3.1 - WordNet Dictionary

adverb

used in negative statement to describe a situation that has existed up to this point or up to the present time (Freq. 9)
- So far he hasn't called
- the sun isn't up yet
• Syn:
so far, thus far, up to now, hitherto, heretofore,
yet, til now, until now