## Wikipedia - انحراف معياري (ar) standard deviation, $$s$$

https://doi.org/10.1351/goldbook.S05911
The positive square root of the sum of the squares of the deviations between the observations and the mean of the series, divided by one less than the total number in the series. The standard @[email protected] is the positive square root of the variance, a more fundamental statistical quantity.
Source:
Orange Book, 2nd ed., p. 5 [Terms] [Book]