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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"
come upon, as if by accident; meet with; "We find this idea in Plato"; "I happened upon the most wonderful bakery not very far from here"; "She chanced upon an interesting book in the bookstore the other day"