Collocations for coincidence - noun

complete, pure, sheer
It was pure coincidence that they were both in Paris on the same day.

mere | happy
What a happy coincidence to meet you at the airport just when I wanted to see you.

unfortunate, unhappy | amazing, curious, extraordinary, funny, incredible, odd, remarkable, strange, wonderful

series, set, string
They met through a series of strange coincidences.

happen
Remarkable coincidences do happen in real life.

by (a) ~
By coincidence, we both went to the same school. | By an unfortunate coincidence, their house was burgled on the day he lost his job.