Coicidence is an ancient islamic saying describing multiple scenrios that are somewhat similar yet distinctly noteworthy. A prime example being 911 which just happens to be the number to '911' (in all seriousness).
The spandex of coincidence can be used a ANALize whether or not two events are different. It does not have to prove a relationship but it does have to prove comparison. The odds that two african monkeys spread the same STD, for example, reaches 50% making this an unrelated exapmle of the word coincidence.
For further information search coincidence.