Longman Dictionary of Contemporary English - coincidence

~ n 1 a surprising and unexpected situation in which two things that are connected happen at the same time, in the same place, or to the same people  (What a coincidence! I didn't know you were going to be in Geneva too! | by coincidence)  (My mother is called Anna, and by a funny coincidence my wife's mother is also called Anna. | be sheer/pure coincidence (=happen completely by chance) | not a coincidence/more than coincidence (=used when you think something did not happen by chance))  (It can't be a coincidence that four jewelry stores were robbed in one night.) 2 formal if there is a coincidence between two ideas, opinions etc, the ideas etc are the same + of  (a coincidence of opinion among the board members)