Meaning of AGO in English
a ‧ go S1 W1 /əˈɡəʊ $ əˈɡoʊ/ BrE AmE adverb
[ Date: 1400-1500 ; Origin: From the past participle of ago 'to pass away' (11-17 centuries) , from Old English agan , from gan 'to go' ]
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.
• • •
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 preposition ('at', 'in', 'on' etc) before a phrase 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).
Longman Dictionary of Contemporary English. Longman - Словарь современного английского языка. 2012