1. At this time; for the present: isn't ready yet.
2. Up to a specified time; thus far: The end had not yet come.
3. At a future time; eventually: may yet change his mind.
4. Besides; in addition: returned for yet another helping.
5. Still more; even: a yet sadder tale.
6. Nevertheless: young yet wise.
conj. And despite this; nevertheless: She said she would be late, yet she arrived on time.
still; until the present time:
I haven't spoken to her yet.
He hasn't finished yet.
"Are you ready?" "Not yet - wait a moment."
from now and for a particular period of time in the future:
She won't be back for a long time yet.
Our holiday isn't for weeks yet.
even at this stage or time:
We could yet succeed - you never know.
You might yet prove me wrong.
He may win yet.
does yet use only in perfect or i can use it in other tenses
You can use it in the following common tenses:
He hasn't read the book yet. (present perfect)
He hadn't read the book yet. (past perfect)
He won't have finished the book yet (future perfect)
Mario doesn't speak English yet. (simple present)
Maria didn't know that yet. (simple past)
The plane isn't leaving yet. (present continuous)
The baby wasn't walking yet. (past continuous)
Note that these are all negative sentences. They can all be formed into questions using 'yet'.
So, you see the actual tense is not really the determinant of whether you can use 'yet' or not. The context is the important factor.
Note that in the simple and continuous past, the 'yet' refers to a time in the past.
There is a form that you might hear but will never have to use. It is sometimes used regionally by some Americans: Did you have your dinner yet? Here, the sentence is in the past simple, but the yet refers to the present. It's probably best avoided by learners, since the standard form (Have you had your dinner yet?) is acceptable everywhere.