Study this example situation:

Ann is looking for her key. She can’t find it. She has lost her key.

Ann is looking for her key. She can’t find it. She has lost her key. - English Grammar - Present perfect (I have done)
Ann is looking for her key. She can’t find it. She has lost her key.

 

“She has lost her key” = She lost it and she still hasn’t got it.

Have/has lost is the present perfect simple:

Have/has lost is the present perfect simple. - English Grammar - Present perfect (I have done)

The present perfect simple is have/has + past participle. The past participle often ended in -ed (finished/decided etc.), but many important verbs are irregular (lost/done/been/written etc.).

When we use the present perfect there is always a connection with now. The action in the past has a result now:

  • “Where’s your key?”  “I don’t know. I’ve lost it.” (I haven’t got it now)
“Where’s your key?” “I don’t know. I’ve lost it.” - English Grammar - Present perfect (I have done)
“Where’s your key?” “I don’t know. I’ve lost it.”

 

  • He told me his name but I’ve forgotten it. (I can’t remember it now)
He told me his name but I’ve forgotten it. - English Grammar - Present perfect (I have done)
He told me his name but I’ve forgotten it.

 

  • “Is Sarah here?”  “No, she’s gone out.” (she is out now)
“Is Sarah here?” “No, she’s gone out.” - English Grammar - Present perfect (I have done)
“Is Sarah here?” “No, she’s gone out.”

 

  • I can’t find my watch. Have you seen it? (do you know where it is now?)
I can’t find my watch. Have you seen it? - English Grammar - Present perfect (I have done)
I can’t find my watch. Have you seen it?

 

We often use the present perfect to give new information or to announce a recent happening:

  • Ow! I’ve cut my finger.
Ow! I’ve cut my finger. - English Grammar - Present perfect (I have done)
Ow! I’ve cut my finger.

 

  • The road is closed. There’s been (= there has been) an accident.
The road is closed. There’s been (= there has been) an accident. - English Grammar - Present perfect (I have done)
The road is closed. There’s been an accident.

 

  • The police have arrested two men in connection with the robbery.
The police have arrested two men in connection with the robbery. - English Grammar - Present perfect (I have done)
The police have arrested two men in connection with the robbery.

 

You can use the present perfect with just, already and yet:

Just = “a short time ago”:

  • “Would you like something to eat?”   “No, thanks. I’ve just had lunch.”
“Would you like something to eat?” “No, thanks. I’ve just had lunch.” - English Grammar - Present perfect (I have done)
“Would you like something to eat?” “No, thanks. I’ve just had lunch.”

 

  • Hello. Have you just arrived?
Hello. Have you just arrived? - English Grammar - Present perfect (I have done)
Hello. Have you just arrived?

 

We use already to say that something happened sooner than expected.

  • “Don’t forget to post the letter, will you?”  “I’ve already posted it.”
“Don’t forget to post the letter, will you?” “I’ve already posted it.” - English Grammar - Present perfect (I have done)
“Don’t forget to post the letter, will you?” “I’ve already posted it.”

 

  • “What time is John leaving?”  “He’s already gone.”
“What time is John leaving?” “He’s already gone.” - English Grammar - Present perfect (I have done)
“What time is John leaving?” “He’s already gone.”

 

Yet = “until now” and shows that the speaker is expecting something to happen. Use yet only in questions and negative sentences:

  • Has it stopped raining yet?
Has it stopped raining yet? - English Grammar - Present perfect (I have done)
Has it stopped raining yet?

 

  • I’ve written the letter but I haven’t posted it yet.
I’ve written the letter but I haven’t posted it yet. - English Grammar - Present perfect (I have done)
I’ve written the letter but I haven’t posted it yet.

 

Note the difference between gone (to) and been (to):

  • Jane is away on holiday. She has gone to Germany. (= she is there now or on her way there)
Jane is away on holiday. She has gone to Germany. - English Grammar - Present perfect (I have done)
Jane is away on holiday. She has gone to Germany.

 

  • Maria is back home from holiday now. She has been to France. (= she has now come back from France)
Maria is back home from holiday now. She has been to France. - English Grammar - Present perfect (I have done)
Maria is back home from holiday now. She has been to France