Capital Sigma Symbol
The capital Greek letter Σ (Sigma) is used in algebra to represent the summation operator.
The capital letter Sigma Σ represents the summation operation in mathematics, often called sum for short. A sum has three parts: an initial value, an end value, and the expression being summed. The summation starts at the initial value and iterates, adding one to the value for each iteration, stopping when the value reaches the end value.
The Greek letter sigma (σ) is used in statistics to represent the standard deviation of a population of values.