The verb tense after "Until"

Question

I asked a related question, which its answer's comments say I can use different tense after "Until", I thought of posting the question in a separate question to get a complete answer.

Which of the following are possible or more natural

• I waited until he left the room, then I entered there
• I waited until he leaves the room, then I entered there
• I waited until he had left the room, then I entered there

I know it could also be the following, but I didn't find a better example with "until". If you know use that.

• I waited for him to leave the room

What about present:

• I am waiting until he comes back
• I am waiting until he will come back
• I wait until he comes back

Or

• I can't help you until I finish/have finished my work

Answer 1

Ahmad, it follows the same rules as the past question. All tenses mentioned can be used in that sentence. However, as it's a past tense and you are telling a past history, using "had" would make it sound more fluent.

I waited until he had left the room, then I entered there.

Now talking about your second question.

I am waiting until he comes back - Right

I am waiting until he will come back - Wrong

I wait until he comes back - Right

Remember, "until" cannot be used followed by the future tense, all the others alternatives are suitable for until, past tense, past continuous, present tense, present continuous, present perfect..

And I waited for him to leave the room also works and sounds good too, and functions with others tenses too:

I was waiting for him to leave the room

I will be waiting for him to leave the room;

I waited for him to leave the room

I have been waiting for him to leave the room.