What does variance mean?
Variance is the degree to which values differ from one another or from an expected value. In general and professional writing, it can mean a discrepancy or spread: “variance in costs,” for example, suggests that costs are not uniform. In statistics, variance is more precisely defined as the average of the squared deviations from the mean, making it a nonnegative measure of dispersion. A large variance indicates that observations are widely dispersed, while a small variance indicates that they cluster closely around the mean. The word is especially common in data analysis, finance, engineering, and quality control, where changes across measurements must be assessed. Variance is usually formal and technical, but it remains clear in general use. The expression “at variance with” means in disagreement with or different from. Although “variation” may sound similar, variance usually emphasizes a quantified amount of difference or a formal statistical concept.
The amount or degree of difference between things or from an expected value; in statistics, a nonnegative measure of the average squared deviation from the mean.
"The researchers reported a high variance in the participants’ response times."
The statistical definition distinguishes variance from the general sense of difference or discrepancy.
To differ from another person, thing, figure, or standard.
"The two estimates variance slightly from the original figure."
This use is rare and formal in modern English; “differ from” is much more common.
The plural is used for separate differences or multiple statistical values.
"Variances in performance across the regional teams were substantial."
Variance turns the familiar idea of spread into a number: the average squared distance from the mean.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does variance come from?
The noun entered Middle English from Anglo-French variance, a form of Old French variance meaning “difference” or “change.” This continued Latin variantia, which was ultimately derived from varius, meaning “different” or “various.” English cognates from the same root include variable, vary, variegated, and various, while the modern statistical sense developed from the word’s established meaning as a difference or spread.
Related word forms
How variance is actually used
Variance is formal and particularly common in statistics, finance, engineering, and quality control. In general writing, it can sound more technical than “difference” or “variation.” The phrase “at variance with” is idiomatic and means “in disagreement with” or “different from.” The verb form is rare; “differ from” is normally preferred.
Easily confused with variance
Variance is an overall measure of spread, especially a statistical quantity, whereas a deviation is an individual difference from a reference point or average.