The present perfect tense

FORM:

It forms with HAVE/HAS + PAST PARTICIPLE.
-Example: I have finished my homework.

The present perfect of the regular verbs it forms adding –ed to the infinitive
-Examples: walk-->walked, listen-->listened...

USE:

To speak about past actions whose results or consequences still in the present.
-Example: He hasn’t eaten anything. He is very hungry.

To speak about actions just finished we use the past simple with the adverb just between the auxiliary and the participle.
-Example: We’ve just had an accident.

To speak about who started in the past and who’s last in the present yet and probably still in the future. To refer at the last of the action we use the prepositions for and since.
•For refers to a period on time (minutes, hours, months, years, etc).
-Example: I’ve been here for thirty minutes.

•Since refers to a moment on time who started the action and it is followed of an oral expression.
-Example: I’ve been here since 3:30 p.m.

To ask about facts or actions that haven’t finished we use the adverbial phrase: How long...?
-Example: How long have you lived in Madrid?

To refer to an action that happened in the past and who have finished.
-Example: She hasn’t visited El Prado.

With the past perfect tense we can use indefinite time adverbs to be more necessary: ever, never, already, yet and still.
•Ever: it uses in interrogative and negative orations.
-Example: Have you ever been to Argentina?

•Never: it uses in negative orations always when the verb isn’t negative.
-Example: No, I have never been to Argentina.

•Already: it uses in affirmative orations to say that the action have happened yet. It goes after the past participle or at the end of the phrase.
-Example: I’ve already seen the film / I’ve seen the film already.

•Yet: it uses in interrogative orations to ask if the action has happened yet. It goes at the end of the phrase.
-Example: Have you finished that exercise yet?

•Still: also goes in negative orations to say that the actions haven’t happened yet. Still is more efficient than yet, and it goes before the auxiliary have/has.
-Example: We haven’t eaten lunch yet.


CREDITS:

Text ~> my own words
Date ~> 24th - January - 2008