---
name: "conj"
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/conj"
---

# conj(3)

calculate the complex conjugate

## NAME

conj, conjf, conjl - calculate the complex conjugate

## LIBRARY

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

## SYNOPSIS

```
#include <complex.h>
```

**double complex conj(double complex** *z***);** **float complex conjf(float complex** *z***);** **long double complex conjl(long double complex** *z***);**

## DESCRIPTION

These functions return the complex conjugate value of *z*. That is the value obtained by changing the sign of the imaginary part.

One has:

```
cabs(z) = csqrt(z * conj(z))
```

## ATTRIBUTES

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

| | | |
| --- | --- | --- |
| **Interface** | **Attribute** | **Value** |
| **conj**(), **conjf**(), **conjl**() | Thread safety | MT-Safe |

## STANDARDS

C11, POSIX.1-2008.

## HISTORY

glibc 2.1. C99, POSIX.1-2001.

## SEE ALSO

[**cabs**(3)](/cabs/3.md), [**csqrt**(3)](/csqrt/3.md), [**complex**(7)](/complex/7.md)