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```{index} single: jn; POSIX function
```
```{index} single: POSIX::jn; Perl function
```

# jn

Bessel function of the first kind, integer order `$n`.

## Synopsis

```perl
my $y = POSIX::jn($n, $x);
```

## Differences from upstream

Fully compatible with upstream POSIX.

## See also

- `j0`, `j1` — fixed-order variants for `$n == 0` and `$n == 1`.
- `yn` — Bessel function of the second kind.