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used to show how far back in the past something happened
5 minutes/an hour/20 years etc ago
Her husband died 14 years ago.
long ago/a long time ago
He should have finished at university long ago, but he kept taking extra courses.
a minute/moment ago
The little girl you saw a moment ago was my niece.
a little/short while ago
Tom got a letter from him just a little while ago.
They moved to a new house some time ago (= a fairly long time ago ) .
We had our bicentenary celebrations not that long ago.
Grammar ago, before, previously
Use ago to say how much time has passed from the time something happened to the present time :
We went to Madrid two years ago.
Use before to say how much time passed from the time something happened to a time in the past :
Her husband had died many years before.
Previously is used in the same way, but is more formal :
The meeting was a follow-up to one that had been held four days previously.
► Use the past tense, not the present perfect, with ago :
I started (NOT I’ve started) a new job a few weeks ago.
► Do not use a 介词 (‘at’, ‘in’, ‘on’ etc) before a 短语 with ago :
They first met fifteen years ago (NOT at/in fifteen years ago).
► Do not use ‘since’ or ‘before’ with ago :
I came to the US two months ago (NOT since/before two months ago).