Present Perfect Tense
The present perfect is used to say what has happened recently and has an effect on the present moment. We often use 'just', 'yet' and 'already' to express the relationship to the present moment.
Examples
Have you seen Mary yet?
They've already had dinner.
She's just been to the dentist's.
The present perfect is also used to express something which has happened up to the present moment of time.
Examples
Have you worked here for a long time?
Peter's lived here since 1987.
She hasn't had much fun this week.
Positive Form
Subject + have + past participle + object(s)
Examples
Peter's lived here since 1987.
We've been very busy today.
Negative Form
Subject + have + not + past participle + object(s)
Examples
I haven't been to class very often this month.
She hasn't had much fun this week.
Question Form
(Wh?) + have + subject + past participle?
Examples
Have you worked here for a long time?
Where have you been?
Present Perfect for Unspecified Past
When speaking about an experience that has happened at an UNSPECIFIED point in time before the present moment use the present perfect.
Examples
I've been to New York three times.
They've lived in many places.
She's studied in London.
NOTE: In this use of the present perfect, we are talking about things that have happened up to the present moment. Whenever you speak about something that has happened up to now without giving a precise point in time, use the present perfect.
Use of 'For', 'Since' and 'How long'
Use 'for' to indicate a duration or period of time.
Examples
He has lived here for seven years.
We have been here for six weeks.
Shirley has played tennis for a long time.
Use 'since' to indicate a specific point in time.
Examples
I've worked here since 2004.
She's gone to dancing lessons since April.
They've been unhappy since they left college.
Use 'How long' in the question form to ask about duration.
Examples
How long have you played the piano?
How long has he worked here?
How long has she been with you?
