Variance
Etymology
From Latin “variantia” (difference), from “variare” (to change). The precise statistical term was coined by Ronald Fisher in 1918 as the squared spread underlying much of modern statistics.
noun · /VAIR-ee-uhns/
A measure of how spread out a set of values is around its average.
What it names
It captures consistency versus volatility — two things with the same average can behave completely differently.
Example
Two funds may both average 7 percent a year, but the one with higher variance swings between boom and loss while the other plods steadily.
Related idea
Variance is the square of the standard deviation; the standard deviation is usually reported because it is in the same units as the data, while variance is the raw mathematical quantity.