
Since + momento concreto de tiempo
I haven't studied since Tuesday.No he estudiado desde el marte
Ever:
Significa "alguna vez". Se usa en oraciones interrogativas y se coloca delante del past participle.
Have you ever studied English
Already :Significa "ya". Se utiliza en las oraciones afirmativas y en algunas interrogativas.
Just:Significa "acabar de". Se coloca entre "to have" y el past participle. I have just studied the lesson.
For + período de tiempo
I have studied for three days.He estudiado durante tres días.
REGULAR: ED EX: STUDY-STUDIES: SHE HAS STUDIED TOO MUCH. PLAY-PLAYED: THEY HAVE PLAYED FOR 3 HOURS. WASH-WASHED: SHE HAS WASHED THE CLOTHES . LIVE-LIVED: HE HAS LIVED HERE SINCE 2000. ETC. WATHC-WATCHED. LOVE-LOVED.
IRREGULAR; CHANGED. EX: BE-BEEN. TAKE-TAKEN: SHE HAS TAKEN HER CLASS. DRINK-DRUNK: THEY HAVE DRUNK TOO MUCH.