# \sum

The ∑ symbol (N-ary summation, U+2211), written as \sum in LaTeX math mode.

https://texform.dev/latex/symbols/sum

## Metadata

| Field | Value |
| --- | --- |
| Topic | [Big operators](https://texform.dev/latex/topics/big-operators) |
| Packages | base |
| Allowed mode | math |
| Glyph | ∑ |
| Unicode | U+2211 N-ARY SUMMATION |
| Delimiter | No |

## Syntax

```latex
\sum
```

Takes no arguments.

## Common tasks

### How to write a sum with limits

```latex
\sum_{n=1}^\infty a_n
```

[Open in Playground](https://play.texform.dev/?input=%5Csum_%7Bn%3D1%7D%5E%5Cinfty+a_n)

### How to write an inline sum

```latex
\sum_{i=1}^n i = \frac{n(n+1)}{2}
```

[Open in Playground](https://play.texform.dev/?input=%5Csum_%7Bi%3D1%7D%5En+i+%3D+%5Cfrac%7Bn%28n%2B1%29%7D%7B2%7D)

### How to write a double sum

```latex
\sum_{i=1}^n\sum_{j=1}^m a_{ij}
```

[Open in Playground](https://play.texform.dev/?input=%5Csum_%7Bi%3D1%7D%5En%5Csum_%7Bj%3D1%7D%5Em+a_%7Bij%7D)

### How to write a sum with a stacked condition

```latex
\sum_{\substack{i,j\\ i\neq j}} a_{ij}
```

[Open in Playground](https://play.texform.dev/?input=%5Csum_%7B%5Csubstack%7Bi%2Cj%5C%5C+i%5Cneq+j%7D%7D+a_%7Bij%7D)

## Usage frequency

15.32% of formulas in the measured corpus contain this entry, rank 1 of 474 entries with frequency data.

## In TeXForm

TeXForm parses this entry as a character leaf mapped to U+2211 (N-ARY SUMMATION).