Friday, April 29, 2011

Present Perfect Tense : Unit 17, for since ago


for and since :
We use for and since to say how long :

-          Mary has been in Rio since Monday.
We use for + a periode of time (four days / two years, etc)  :

 

Compare:
-          Dan has been in Canada since January. ( = from January to now)
-          Dan has been in Canada for six months. (not “since six months”)
-          I’ve known her since 1990. (= from 1990 to now)
-          I’ve known her for a long time. (not “since a long time”)
Ago = before now :
-          Sue started her new job two weeks ago. (=two weeks before now)
-          “When did Tom go out?”     Ten minutes ago.” (=ten minutes before now)
-          I had dinner an hour ago. (= an hour before now.)
-          Life was very different a hundred years ago.
We use ago with the simple past (did/had/started, etc.)
Compare ago and for :
-          When did she arrive in Rio?
She arrived in Rio for foiur days.
-          How long has she been in Rio?
She has been in Rio for four days.

For the present perfect + for and since, see Unit 16.

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