English Grammar Rules

The Present Perfect Tense is formed using the following structure:
Affirmative: Subject + Have / Has + Past Participle
Negative: Subject + Haven't / Hasn't + Past Participle
Question: Have / Has + Subject + Past Participle

Affirmative Sentences

Subject	Have	Past Participle	Rest of the Sentence
I	have	studied	for the exam.
You	have	bought	a new computer.
He	has	eaten	my chocolate.
She	has	written	an e-mail.
It	has	been	cold this month.
We	have	won	the championship.
You	have	tried	to learn a lot.
They	have	forgotten	my birthday.

Contractions

The contracted form of the perfect tense is quite common:

Have	Contraction	Examples
I have	I've	I've spent all my money.
You have	You've	You've worn that dress before.
He has	He's	He's slept all morning.
She has	She's	She's lost her purse.
It has	It's	It's fallen off the wall.
We have	We've	We've chosen you for the job.
You have	You've	You've begun to annoy me.
They have	They've	They've drunk too much.

We use contractions a lot when we are speaking.

Negative Sentences

The contraction of the perfect tense in negative form is:
Have not = Haven't
Has not = Hasn't

Subject	Have	Past Participle	Rest of the Sentence
I	haven't	studied	for the exam.
You	haven't	bought	a new computer.
He	hasn't	eaten	my chocolate.
She	hasn't	written	an e-mail.
It	hasn't	been	cold this month.
We	haven't	won	the championship.
You	haven't	tried	to learn a lot.
They	haven't	forgotten	my birthday.

Questions

Have	Subject	Past Participle	Rest of the Sentence
Have	I	been	chosen for the team?
Have	you	bought	a new car?
Has	he	eaten	my sandwich?
Has	she	written	the letter?
Has	it	started	on time?
Have	we	won	a trophy?
Have	you	kept	my secret?
Have	they	driven	there?

When do we use the Present Perfect Tense?

1. Unspecified point in the past

• I have been to Spain three times.
  (At some unspecified time in the past, I went to Spain).

Compare with the simple past:

• I went to Spain three times in 2005.
  (specified time in the past - the year 2005)

2. An action that occurred in the past, but has a result in the present (now)

• We can't find our luggage. Have you seen it?
  (The luggage was lost in the past, do you know where it is now?)

3. Talking about general experiences (ever, never)
It usually refers to an event happening at some moment in your life.

• Has she ever tried Chilean wine before? (in her life)
• I've never eaten monkey brains before. (in my life)

4. Events that recently occurred (just)

• Do you want to go to a restaurant with me?
  No, thanks. I've just eaten lunch. (I recently ate lunch.)

5. Events that have occurred up to now (yet)

• Are Carlos and Rodrigo here? No, they haven't arrived yet. (they're still not here now)

6. Events that occurred before you expected (already)

• I've already graduated from University. (I expected to graduate at a later date.)

7. Events that began in the past and haven't changed (for, since)

• Mike has worked at Woodward for 3 years.
  (Mike started working at Woodward 3 years ago and he still works there now.)
• Julie has worked at Woodward since September last year.
  (Julie began working at Woodward in September of last year, and that hasn't changed - she still works here now.)