1. For any event A, 0 ≤ P(A) ≤ 1.

2. P(impossible event) = 0.

Also written P(empty set) = 0 or P() = 0.

3. P(sure event) = 1.

Also written P(S) = 1, where S is the sample space.

4. P(not A) = 1 – P(A).

Also written P(complement of A) = 1 – P(A) or P(A^{C}) = 1 – P(A) or .