Present Perfect

 

We use the present perfect simple tense to talk about an action in the past that has a result now.   

The present perfect simple tense is often used with the words just, already and yet. The words just and already come between the auxiliary verb have and the main verb. The word yet comes at the end of the sentence.

I have just seen a brilliant film.
They have already told me about it.
Mark has not arrived yet.

We normally use just and already in positive statements.

We normaly use yet in questions and negative statements. 

We use ever in questions and never to make a statement.

Have you ever been to the USA?

Mary has never been to Canada.