PRESENT PERFECT
We use the Present Perfect to say that an action happened at an unspecified time before now. The exact time is not important. You CANNOT use the Present Perfect with specific time expressions such as: yesterday, one year ago, last week, when I was a child, when I lived in Japan, at that moment, that day, one day, etc. We CAN use the Present Perfect with unspecific expressions such as: ever, never, once, many times, several times, before, so far, already, yet, etc.
FORMS
Affirmative:S+to have+V(in the third form)/-ed(regular verbs)
For Example:I have gone to school.
Paul has listened to music.
Interogative:Have/Has+S+V(in the third form)/-ed(regular verbs)
For Example:Have I gone to school?
Has Paul listened to music?
Negative:S+to have+NOT+V(in the third form)
For Example:I have not gone to school.
ADVERBS OF TIME:
already,just
I have already watched this film.
He has just drunk a cup of tea.
for,since
for=>duration of time
since=>exact time
For Example:for 2 days,since Tuesday,10.am
yet
I haven't read this book yet.
