In its specific meaning, variance refers to a statistical measurement reflecting the expected deviation between values in a specific data set. In probability theory and statistics, variance is the expected value of the squared deviation from the mean of a random variable. The standard deviation (SD) is calculated as the square root of the variance. The variance measures the average degree to which each data item or point deviates from the mean. While standard deviation is the square root of the variance, variance is the average of all data points within a data set.

In a broader context, variance represents the difference between planned and actual results or figures. For example, variance may arise between planned and actual expenses due to certain reasons including unexpected expenses.