Source

File: wp-includes/taxonomy.php

function wp_count_terms( $taxonomy, $args = array() ) {
	$defaults = array(
		'taxonomy'   => $taxonomy,
		'hide_empty' => false,
	);
	$args     = wp_parse_args( $args, $defaults );

	// Backward compatibility.
	if ( isset( $args['ignore_empty'] ) ) {
		$args['hide_empty'] = $args['ignore_empty'];
		unset( $args['ignore_empty'] );
	}

	$args['fields'] = 'count';

	return get_terms( $args );
}