there was an occurance when a boy broke his leg

Sometimes defines an infrequent occurance.

Often defines a frequent occurance.

The chance of occurance

when the occurance of an event B is not affected by the occurance of event A than we can say that these events are not dependent with each other

1. Contingent liability is a liability the occurance or some information of which is dependable on the occurance of any future incidend until that liability is not confirmed