3 Definitions

A measure of deviation from the mean in a sample or population
defined by 6SixSigSigma
a specifically defined mathematical measure of variability in a data set or population. The variance is the standard deviation squared. Variance should not be confused with variability, which refers to the characteristic of a process to take on different values when it is repeated.
A measure of the spread of a probability distribution. The square of the standard deviation. See statistics texts.