Σ (Greek letter)

The Greek letter Σ (Sigma) is used in mathematics to indicate summation, which means adding together a series of numbers or expressions. When you see Σ, it usually comes with a label showing where to start and end the addition. For example, \(\Sigma_{i=1}^{5} i\) means "add all the values of \(i\) from 1 to 5," which is 1 + 2 + 3 + 4 + 5, totaling 15. Sigma helps efficiently represent the process of adding many values without listing each one individually.