sigma
n. countablen. the eighteenth letter of the Greek alphabet. In math and science, it is often used as a symbol for a specific sum or a measurement of how spread out data is.
n. the eighteenth letter of the Greek alphabet, represented as Σ (upper case) or σ (lower case). It serves as a standard symbol for summation in mathematics and for standard deviation in statistics.
The sigma symbol represents the sum of all the numbers.
In the final report, the researcher used the lower-case sigma to indicate the standard deviation of the test results.
The Greek letter sigma is ubiquitous in technical literature, appearing as a summation operator in calculus and as a measure of volatility in financial risk assessment models.
When used as a mathematical operator, it is typically followed by a variable or expression.