I know that we use "yet" with Present Perfect in interrogative and negative sentences. And "already" is used in affirmative statements. Despite that fact I have found one sentence:
"What have you already done today?"
Is it correct?
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Sign up to join this communityI know that we use "yet" with Present Perfect in interrogative and negative sentences. And "already" is used in affirmative statements. Despite that fact I have found one sentence:
"What have you already done today?"
Is it correct?
An NPI (negative polarity item) is a term restricted to negative contexts, and a PPI (positive polarity item) is one restricted to positive contexts.
Yet is the NPI corresponding to the PPI already.
Questions may be positive or negative; for instance, if you are asking about the status of a completed task:
Haven't you done that yet? is what you would ask if you expected the task to be finished but had reason to believe that it was not.
Have you done that yet? is what you would ask if you had no expectation and no evidence that in fact it was completed.
Have you done that already? is what you would ask if you expected the task to be unfinished but had evidence that in fact it was finished.
In your example, the question is positive: it asks about what you have done, not what you have left undone.
The question is correct.
"Already" means "before now" and suggests that the fact is at least a little surprising or exceeds normal expectation, or at least is some new information to the person spoken to. Often, it means that something's not necessary, because it's been taken care of before now.
Asking "Have you already brushed your teeth?" suggests that I was going to ask you to brush your teeth, but if you've already brushed them, it's not necessary now.
"What have you already done today?" suggests that I want to know what you've done today, with a sense that it's no longer necessary, or that it was done sooner than normal.
Both "Have you done that already?" and "Have you done that yet?" are Present Perfect, but the "already" example is about a result of a past action (you've done it, so it's finished), and the "yet" example is reviewing the time up to now and asking whether you did something in that time.
Also, you may find "already" added to a question or command to express impatience. This is a little different and "already" usually comes at the end.
You can often judge whether this other meaning is intended from tone and/or context. It can sound rude when the speaker isn't already on familiar speaking terms.