Present perfect (by mpf97)

Presnt Perfect

Form[has/have + past participle]

I have done my homeworkWe haven't seen him for agesHave you met her before?

Signal Wordsjust, yet, never, already, ever, so far, up to now, recently, since and for.

for a period(from start to end)>===< since a point(up to now)x===>|

They study for two hours every dayHe has been here since 9am.

Past simple vsPresent perfect