<!-- GENERATED by docs/sphinx/bin/02-reference from POSIX.rs (xs_yn). Do not edit. -->

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

# yn

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

## Synopsis

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

## Edge cases

- `yn($n, 0)` returns negative infinity (the function has a
  singularity at zero).

## Differences from upstream

Fully compatible with upstream POSIX.

## See also

- `y0`, `y1` — fixed-order variants.
- `jn` — Bessel function of the first kind.