Present perfect

PRESENT PERFECT

FORM
Has/have + past participle |
We use the Present Perfect to say that an action happened at an unspecified time before now. The exact time is not important. You CANNOT usethe Present Perfect with specific time expressions such as: yesterday, one year ago, last week, when I was a child, when I lived in Japan, at that moment, that day, one day, etc. We CAN use the PresentPerfect with unspecific expressions such as: ever, never, once, many times, several times, before, so far, already, yet, etc.

Structure Affirmative, Negative and Interrogative

Positive |Subject | To have | Past participle |
She | has | Finished. |
Negative |
Subject | To have + not | Past participle |
She | Hasn’t | Finished. |
Interrogative positive |
To have | Subject |Past participle |
Has | she | Finished…? |
Interrogative negative |
To have + Not | Subject | Past participle |
Hasn’t | she | Finished…? |

Examples:
* I have seen that movie twentytimes.
* I think I have met him once before.
* There have been many earthquakes in California.
* People have traveled to the Moon.
* People have not traveled to Mars.
* Have you readthe book yet?
* Nobody has ever climbed that mountain.
* A: Has there ever been a war in the United States?
B: Yes, there has been a war in the United States.

PRESENT PERFECT VS SIMPLEPAST
Simple Past | Present Perfect |
Irregular verbs: see 2nd column of irregular verbsExample:I spoke | Irregular verbs: form of 'have' + 3rd column of irregular verbsExample:I / you / we / theyhave spokenhe / she / it has spoken |
| |
Regular verbs: infinitive + edExample:I worked | Regular verbs: form of 'have' + infinitive + edExample:I / you / we / they have workedhe / she / ithas worked |
I phoned Mary 2 minutes ago. I have just phoned Mary.
He went to Canada last...