The function is called the probability mass function of the random variable .

For the cumulative distribution function one has .

The probability of the complement event of is .

For any two events and one has .

If are events, then occurs if both events occur.

Let be a 3-dimensional bounded region and its boundary the surface . If is a continuously differentiable vector field, then

The scalar function is called the potential of the vector field if .

The function has a local maximum at if there exists such that for any .

If the directional derivative of the function in the direction at is negative, then moving from in the direction the function is decreasing.

The function is differentiable at if there exists a linear map such that