Study this example:
- John: Have you heard from Tom?
- Jane: No, he hasn't sent me an email lately.
We use the present perfect tense when we talk about a period of time that continues up to the present. John and Jane are talking about the period between a short time ago and now. Therefore, they say "Have you heard" and "he hasn't sent ...".
Here are some more examples:
- Have you seen my bag? I can't find it anywhere.
- Everything is going fine. We haven't had any problem so far.
- We have seen a lot of interesting people in the last few days.
- Martin has been sick a lot in the past few years, hasn't he?
- I haven't seen Julia recently. Have you?
We often use the present perfect tense with "yet". "Yet" shows that the speaker is expecting something to happen.Use "yet" only in questions and negative sentences:
- Has it stopped raining yet?
- I haven't told them about the accident yet.
You can also use "yet" with the simple past tense:
- Did it stop raining yet?
- I didn't tell them about the accident yet.
We use the present perfect tense with "this morning / this evening / today / this week / this semester / etc." when these periods are not finished at the time of speaking:
- I've had three cups of coffee today. (Perhaps I'll have more before the day is over)
- Has Jane had vacation this year?
- I haven't seen Tom this morning. Have you?
- Ann hasn't studied very much this semester.
- George is calling his girlfriend again. That's the third time he's called her this morning.