# \abs

Used for absolute values in the physics package, with a required brace-delimited expression and optional starred plain fences.

https://texform.dev/latex/commands/abs

## Metadata

| Field | Value |
| --- | --- |
| Topic | [Physics: quantities](https://texform.dev/latex/topics/physics-quantities) |
| Packages | physics |
| Allowed mode | math |
| Tags |  |
| Commonality | medium |
| Kind | prefix |

## Syntax

### physics

Argument specification: `s m{}`

Used for absolute values in the physics package, with a required brace-delimited expression and optional starred plain fences.

## Examples

```latex
\abs{a}
```

[Open in Playground](https://play.texform.dev/?input=%5Cabs%7Ba%7D)

```latex
\abs*{a}
```

[Open in Playground](https://play.texform.dev/?input=%5Cabs*%7Ba%7D)

## Renderer support

| Package | MathJax | KaTeX | XeTeX |
| --- | --- | --- | --- |
| physics | full | none | full |

## In TeXForm

TeXForm parses this entry as prefix syntax; the package determines its argument specification.

### Expands to (physics)

```latex
\abs{#1}
```

→

```latex
\left| #1 \right|
```

With a leading star, the reparsed form uses plain fences `| #1 |`; with an adjacent sizing control sequence \big, \Big, \bigg, or \Bigg before the brace, it reparses to the corresponding sized fence form.

### [physics/abs-to-vert-fence](https://texform.dev/rules/physics/abs-to-vert-fence)

Rewrite abs to explicit vertical bar fences.

Level: faithful. Fidelity: render.

```latex
\abs{#1}
```

→

```latex
\left| #1 \right|
```

```latex
\abs{x-y}<\varepsilon
```

→

```latex
\left| x-y \right|<\varepsilon
```

## Equivalent forms

```latex
\absolutevalue{#1}
```

exact. MathJax maps both names to the same parse method with the same parameters, including star and sized-prefix behavior.

## See also

- [\\absolutevalue](https://texform.dev/latex/commands/absolutevalue)
- [\\bqty](https://texform.dev/latex/commands/bqty)
- [\\Bqty](https://texform.dev/latex/commands/Bqty)
- [\\norm](https://texform.dev/latex/commands/norm)
- [\\order](https://texform.dev/latex/commands/order)
- [\\pqty](https://texform.dev/latex/commands/pqty)
- [\\qty](https://texform.dev/latex/commands/qty)
- [\\quantity](https://texform.dev/latex/commands/quantity)
- [\\vqty](https://texform.dev/latex/commands/vqty)

## Test cases

### physics

| Input | Case | MathJax | KaTeX | XeTeX |
| --- | --- | --- | --- | --- |
| \abs{a} | Positive: baseline | Pass | Fail | Pass |
| \abs*{a} | Positive: vary:s[0] | Pass | Fail | Pass |