Definition: 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

Usage:the probability that an unbiased coin will fall with the head up is 0.5

Definition: come upon, as if by accident; meet with

Usage: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