Perfekti – Present Perfect
Perfektiä käytetään ilmaisemaan toimintaa, joka on alkanut menneisyydessä ja jatkuu edelleen. Perfekti muodostetaan apuverbistä have tai has ja pääverbin kolmannesta muodosta. Säännöllisen verbin kolmas muoto saadaan lisäämällä pääte -ed: work – worked. Epäsäännöllisen verbin kolmas muoto on opeteltava ulkoa: go – went – gone.
The present perfect simple expresses an action that is still going on or that stopped recently, but has an influence on the present. It puts emphasis on the result.
For something that started in the past and continues in the present:They’ve been married for nearly thirty years.
For something we have done several times in the past and continue doing:She has written five books and she is working on another one.
With 'since' to show when something started in the past:We have worked here since we left school.
When we are talking about our experience up to the present:Her last birthday was the worst day she has ever had.
For something that happened in the past but is important at the time of speaking:Jane isn’t at home. I think she has gone to school.
* Present perfect of 'to be' when someone has gone to a place and returned:
* But when someone has not returned we use 'have/has gone':
A: Where have you been?
B: I’ve just been out to the library.
A: Where is Angel? I haven’t seen her for days.
B: She's gone to London for a week. She’ll be back tomorrow.
Form: have/has + past participle  
I, you, we, theyhave told.haven't told.Have you told?
He, she, ithas told.hasn't told.Has she told?
Past participle
Irregular verbs
You have to know all forms of the irregular verbs very well. For the past participle you need the form of the verb which can be found in the 3rd column of the table of the irregular verbs
go – went – gone
Regular verbsadd -ed
work – worked
Sometimes there are exceptions in spelling when adding -ed.
Consonant after a short, stressed vowel at the end of the wordDouble the consonant:
stop – stopped
swap – swapped
In British EnglishDouble one -l at the end of the word:travel – travelled
One -e at the end of the word
Leave out the -e. Add -d:
love – loved
save – saved
Verbs ending in -y
Verbs ending in -y preceded by a vowel (a, e, i, o, u) Add -ed:play – played
Change 'y' to 'i' after a consonant. Then add -ed:worry – worried
Signal words: 'already', 'ever', 'just', 'never', 'not yet', 'so far', 'till now', 'up to now'.
Ever and neverBefore the main verb (past participle).
AlreadyBefore the main verb (past participle) or at the end of the sentence.
YetPlaced at the end of the sentence.