What Greek letter is used to signify summation?

The Greek letter used to signify summation is Sigma. Sigma represents the sum of a series of terms in mathematics. It is commonly used to represent the idea of adding up a sequence of numbers or variables. The uppercase Sigma (∑) is used to indicate the sum of multiple terms, starting from a specific value and ending at another value, while the lowercase sigma (σ) is often used to represent standard deviation. Overall, Sigma is a widely recognized symbol in mathematics to denote summation.