You can get it like this
$terms = get_terms("my_taxonomy");
$count = count($terms);
if ( $count > 0 )
{
echo "<ul>";
foreach ( $terms as $term )
{
echo "<li>" . $term->name . "</li>";
}
echo "</ul>";
}
Otherwise you can also use like this
$term_slug = get_query_var( 'term' );
$taxonomyName = get_query_var( 'taxonomy' );
$current_term = get_term_by( 'slug', $term_slug, $taxonomyName );
$args_list = array(
'taxonomy' => 'item', // or use $taxonomyName for all taxonomies
'show_count' => true,
'hierarchical' => true,
'child_of' => $current_term->term_id,
'hide_empty' => '0',
'title_li' => '',
'echo' => '0',
);
echo wp_list_categories($args_list);