Sum (LaTeX symbol)

This command generates the summation operator,

$\sum$ . The difference between this and \Sigma, which generates the capital letter

$\Sigma$ , is that \sum appears larger, and that it supports the limits to be displayed below and above the symbol.

The following example illustrates the difference between \sum and \Sigma.

$\sum _{n=1}^{\infty }{\frac {1}{2^{n}}}=1\qquad \Sigma _{n=1}^{\infty }{\frac {1}{2^{n}}}=1$

This examples are written as:

\sum_{n=1}^\infty\frac{1}{2^n}=1
\qquad
\Sigma_{n=1}^\infty\frac{1}{2^n}=1