Present Perfect Tense

We use the present perfect:

· For an action which started in the past and continues up to the present, especially with stative verbs such as be, have, like, know, etc. I have known Dave for years.

· For a recently completed action whose result is visible in the present. A new French restaurant has just opened in Bridge Street. We're going there for dinner tomorrow.

· For an action that happened at an unstated time in the past. The emphasis is on the action. The time that it occurred is unimportant or unknown. I have visited Portugal. (When? Unstated time.)

Note:

already is used in statements after the auxiliary verb and in questions after the main verb. I have already finished. Have you finished already?
yet is used in negative sentences after a negative contracted auxiliary verb or at the end of the sentence. She hasn’‘t yet finished the report. She hasn't finished the report yet.
still is used in statements and questions after the auxiliary verb or before the main verb. I am still painting thehouse. He still lives in Hong Kong.
However, still comes before the auxiliary verb in negations. She still hasn't finished her homework.

Time expressions used with the present perfect: for, since, already, always, just, ever, never, so far, today, this week/month etc, how long, lately, recently, still (in negations), etc.

Present Perfect- Continuous Tense

We use the present perfect continuous:

· To put emphasis on the duration of an action which started in the past and continues up to the present, used with action verbs and with words and expressions such as for, since, all morning/day/year and How long? The boys have been playing football for hours.

· For an action which started in the past and which lasted for some time. The action may still be continuing or have finished already with the result visible in the present. For this situation two sentences are used. Ken is really tired. He has been working hard all week.

· To express anger, irritation, or annoyance. They have been listening to that loud music all night.

· For repeated actions in the past continuing to the present. I have been taking Spanish lessons at night school.

Note:

With the verbs live, work, teach and feel we can use the present perfect or the present perfect- continuous with no difference in meaning. He has taught/has been teaching at the school for more than twenty years.