---
name: "gamma"
section: "3"
platform: "linux"
package: "man-pages"
version: "6.19-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux", "freebsd"]
url: "https://new.carta.tech/gamma"
---

# gamma(3)

(logarithm of the) gamma function

## NAME

gamma, gammaf, gammal - (logarithm of the) gamma function

## LIBRARY

Math library (*libm*, *-lm*)

## SYNOPSIS

```
#include <math.h>
```

**\[\[deprecated\]\] double gamma(double** *x***);** **\[\[deprecated\]\] float gammaf(float** *x***);** **\[\[deprecated\]\] long double gammal(long double** *x***);**

Feature Test Macro Requirements for glibc (see [**feature\_test\_macros**(7)](/feature_test_macros/7.md)):

**gamma**():

```
    _XOPEN_SOURCE
        || /* Since glibc 2.19: */ _DEFAULT_SOURCE
        || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
```

**gammaf**(), **gammal**():

```
    _XOPEN_SOURCE >= 600 || (_XOPEN_SOURCE && _ISOC99_SOURCE)
        || /* Since glibc 2.19: */ _DEFAULT_SOURCE
        || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
```

## DESCRIPTION

These functions are deprecated: instead, use either the [**tgamma**(3)](/tgamma/3.md) or the [**lgamma**(3)](/lgamma/3.md) functions, as appropriate.

For the definition of the Gamma function, see [**tgamma**(3)](/tgamma/3.md).

### \*BSD version

The libm in 4.4BSD and some versions of FreeBSD had a **gamma**() function that computes the Gamma function, as one would expect.

### glibc version

glibc has a **gamma**() function that is equivalent to [**lgamma**(3)](/lgamma/3.md) and computes the natural logarithm of the Gamma function.

## RETURN VALUE

See [**lgamma**(3)](/lgamma/3.md).

## ERRORS

See [**lgamma**(3)](/lgamma/3.md).

## ATTRIBUTES

For an explanation of the terms used in this section, see [**attributes**(7)](/attributes/7.md).

| | | |
| --- | --- | --- |
| **Interface** | **Attribute** | **Value** |
| **gamma**(), **gammaf**(), **gammal**() | Thread safety | MT-Unsafe race:signgam |

## STANDARDS

None.

## HISTORY

SVID 2.

Because of historical variations in behavior across systems, this function is not specified in any recent standard.

4\.2BSD had a **gamma**() that computed ln(\|Gamma(\|*x*\|)\|), leaving the sign of Gamma(\|*x*\|) in the external integer *signgam*. In 4.3BSD the name was changed to [**lgamma**(3)](/lgamma/3.md), and the man page promises

"At some time in the future the name gamma will be rehabilitated and used for the Gamma function"

This did indeed happen in 4.4BSD, where **gamma**() computes the Gamma function (with no effect on *signgam*). However, this came too late, and we now have [**tgamma**(3)](/tgamma/3.md), the "true gamma" function.

## SEE ALSO

[**lgamma**(3)](/lgamma/3.md), [**signgam**(3)](/signgam/3.md), [**tgamma**(3)](/tgamma/3.md)