まだ～ていない・
まだ with a negative verb says that an expected action or change has not happened yet. The situation before that expected endpoint is still continuing.
The situation has not reached its endpoint
まだ points to continuation. With a negative verb, it means that the earlier situation continues because an expected action or change has not happened. It normally leaves open the possibility that the action will happen later.
Actions and changes not completed yet
The most reliable examples have a clear endpoint, such as finishing, submitting, or starting.
Only the verb changes
まだ itself never changes. Politeness and time are shown by the verb: まだ終わっていない is plain, まだ終わっていません is polite, and まだ終わっていなかった refers to a past point at which it was not yet finished.
Using a simple negative verb
A simple negative is natural when the context clearly supplies an expected time or future step.
A useful short answer
The full action does not need to be repeated because it is clear from the question.
Not yet versus already
まだ with a negative verb places the situation before completion. もう with a past affirmative verb places it after completion.
午前九時にはまだ準備が終わっていなかったが、十時にはもう終わった。
At nine in the morning, the preparations were not finished yet, but by ten they were already finished.
AnalyzeMore examples
田中さんはまだ来ていません。
Tanaka hasn't arrived yet.
Analyzeその本はまだ読み終わっていない。
I haven't finished reading that book yet.
Analyze赤ちゃんはまだ寝ていません。
The baby hasn't gone to sleep yet.
Analyze開始時刻まであと十分あるので、会議はまだ始まらない。
There are still ten minutes until the scheduled start, so the meeting won't begin yet.
Analyzeパスポートはまだ届いていません。
The passport hasn't arrived yet.
Analyze宿題はまだできていません。
My homework isn't done yet.
Analyze昨日の午後三時には、結果はまだ出ていなかった。
At three yesterday afternoon, the results had not come out yet.
Analyze