formalused to say that someone has not done something, or that something has not happened when you think it should already have been done or have happened:
I have yet to hear Ray's version of what happened.
The bank has yet to respond to our letter.
GRAMMAR GRAMMAR In spoken English, yetusually comes at the end of the clause• I haven't finished my homework yet. • We don't know whether she'll come yet.It can also come after 'don't', 'hasn't' etc, or before 'why', 'whether' etc• They don't yet know the full facts.• I haven't decided yet whether to take part in the competition.In writing or more formal speech, yetcan come after 'not'• We do not yet have a solution to this problem.WORD CHOICE: yet, still, alreadyYetis used to say that something has not happened or a situation has not started to exist, or to ask if something has happened• It isn't time to go yet. • Have you seen him yet?Stillis used to say that an earlier situation has not changed• My parents were still asleep (NOT yet asleep). • I still don't understand.Alreadyis used to emphasize that something has happened or a situation has started to exist• He had already published two novels.• They already knew one another.It is also used in questions to show surprise that something has happened sooner than expected• Have you been there already?
Definition from the Longman Dictionary of Contemporary English Advanced Learner's Dictionary.