From+Randomness+to+Probability

The __probability__ of an event is its long run relative frequency. For example, when flipping a coin, in the long run it is expected that the outcomes will be split evenly between heads and tails. The law of large numbers is related to probability by stating: the long run relative frequency of repeated independent events gets closer and closer to the true relative frequency as the number of trials increases. Independent events are two outcomes that don't affect the outcome of the other.