sigma experimental gismu

x1 is the standard variation of/in data set/distribution x2; x1 is the quantified (in)accuracy of the results x2 given by some observation or measurement (procedure), calculated from/by standard x3

Technically, there really is only one possible standard deviation, but in practice, it is often approximate via some means x3 (such as assuming that the distribution is Gaussian, even if it actually is only a finite data sample x2).

In definition:

trinary mathematical operator: [sigma summation of a using variable b over range c].
x1 is the sigma summation of expression x2 with variable x3 over domain x4.

In notes:

soi'auroi (comp!)
almost never/nowhere (default: time sense)
x1 (li) is the (signed) difference between the average of all elements/data of x2 (completely specified ordered multiset/list) and single number x3 (li; default: infimum of x2 under ordering x6 if such is finite), using averaging function x4 (default: arithmetic average), weights x5 (completely specified ordered multiset/list with the same cardinality/length as x2; default: according to notes), and inherited ordering x6 (default: standard ordering on the set of reals).
x1 (data-set, sequence, list) is heteroskedastic by standard x2.
x1 (data-set, sequence, list) is homoskedastic by standard x2.
gau'a (exp!)
mekso (no-more-than-4-ary) operator: Gaussian function f(x, a, b, c) = c e-((x-a).