Present perfect

We use present perfect to express a completed action in the past. The time when the action took place is undefined.

Example:

I have been to Europe.

My sister has eaten lobster.

We also use present perfect to express an action that began in the past and still continues in the present.

Example:

You have studied English for 3 semesters.

I have been in my classroom for 3 hours.

Affirmative pattern

Subject + have/has + verb in past participle + complement

I have written a book

She has given a lecture.

They have seen an accident.

Negative pattern

Subject + haven´t/ hasn´t + verb in past participle + complement

You haven´t drunk wine.

He hasn´t bought a new car.

We haven´t won any competition.