**(1) **The quality of being probable; a probable event or the most probable event

"For a while mutiny seemed a probability"

"Going by past experience there was a high probability that the visitors were lost"

**(2) **A measure of how likely it is that some event will occur; a number expressing the ratio of favorable cases to the whole number of cases possible

"The probability that an unbiased coin will fall with the head up is 0.5"