P(A|B) stands for "the conditional probability of A given B", or "the probability of A under the condition B", i.e. the probability of some event A under the assumption that the event B took place.
The Joint probability is the probability of two events in conjunction. That is, it is the probability of both events together. There are three notations for the joint probability of A and B. It can be written as
- P(A ∩ B)
- P(AB) or
- P(A,B)
The conditional probability is defined by