$p = pdf( $x, $m, $s );

##</code><code>##

$prob_density = pdf( $x, $mean, $std_dev );

##</code><code>##

$prob_density = pdf( { x => $x, mean => $mean, std_dev => $std_dev } );
$prob_density = pdf( { z => $z } ) / $std_dev;