Events for which the occurrence or non-occurrence of one affects the probability of the occurrence of the other.
Example
A bag contains 10 red marbles and 20 white marbles. We draw two marbles from the bag randomly and one after the other, without putting them back after each draw. The event A: “drawing a white marble on the first draw” and event B: “drawing a red marble on the second draw” are dependent events, because the probability of event B depends on the result from the first draw (white marble or red marble).