/ kəʊˈɪnsɪdəns; NAmE koʊ-/ noun
1.
[ C , U ] the fact of two things happening at the same time by chance, in a surprising way :
a strange / an extraordinary / a remarkable coincidence
What a coincidence! I wasn't expecting to see you here.
It's not a coincidence that none of the directors are women (= it did not happen by chance) .
By (sheer) coincidence , I met the person we'd been discussing the next day.
➡ note at luck
2.
[ sing. ] ( formal ) the fact of things being present at the same time :
the coincidence of inflation and unemployment
3.
[ sing. ] ( formal ) the fact of two or more opinions, etc. being the same :
a coincidence of interests between the two partners
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WORD ORIGIN
early 17th cent. (in the sense occupation of the same space ): from medieval Latin coincidentia , from coincidere coincide, agree, from co- together with + incidere fall upon or into.