started this presentation.
YET is used to talk about something
which is expected to happen. It means ‘at any time up to now’.It is used in questions and negatives.
Have you been to London YET?
No, I haven't been to London YET.
ALREADY is used to say that something has happened early or earlier than it might have happened.
I have ALREADY been to Brazil.
STILL is used to talk about something that hasn’t finished – especially when we expected it to finish earlier.
The pizza we’ve ordered still hasn’t arrived.