ago

UK: /əˈgəʊ/ US: /əˈgoʊ/ ,(ə gō′)

WordReference Random House Learner's Dictionary of American English © 2026

a•go /əˈgoʊ/   adj. [after a noun]

1. gone by;
   past:
   She got here five days ago.

adv. 

2. in the past:
   It happened long ago.

WordReference Random House Unabridged Dictionary of American English © 2026

a•go  (ə gō′), adj. 

1. gone;
   gone by;
   past (usually prec. by a noun):
   five days ago.

adv. 

2. in past time;
   in the past:
   All this happened long ago.

• Middle English ago(n), Old English āgān, past participle of āgān to go by, pass, equivalent. to ā- a-³ + gān to go¹ bef. 1000

Collins Concise English Dictionary © HarperCollins Publishers::

ago / əˈɡəʊ/ adverb

1. in the past: five years ago, long ago

Etymology: 14th Century ago, from Old English āgān to pass awayUSAGE
The use of ago with since (it's ten years ago since he wrote the novel) is redundant and should be avoided: it is ten years since he wrote the novel