An operator that combines multiple terms or elements through addition in series and sequences.
Examples
Basic summation of sequence
\sum_{i=1}^{n} i = \frac{n(n+1)}{2}
Double summation with limits
\sum_{i=1}^{m} \sum_{j=1}^{n} a_{ij}
Infinite series with condition
\sum_{n=0}^{\infty} \frac{1}{2^n} = 2