Technically, possibility of any event is always 1 or 0 i.e. ‘yes’ or ‘no’. If an event is possible, how likely will its occurrence be, under a given situation is probability.
Example, When we roll a dice, possibility of it showing up number 5 is ‘Yes’ (or 1), possibility of showing up number 8 is ‘No'(or 0).In a situation where the dice is rolled once, Probabilty of it showing up number 5 is 1/6.
So, every event that we consider while finding the probability of occurence of a particular event, is a possible event.

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