使用“parent”参数：

http://codex.wordpress.org/Function_Reference/get_terms

http://codex.wordpress.org/Function_Reference/get_categories

对于woocommerce电子邮件模板，请使用以下内容：

$terms = get_the_terms( $_product->id , \'product_cat\');
    if($terms) {
        foreach( $terms as $term ) {
            $term = get_term_by("id", $term->parent, "product_cat");
            if ($term->parent > 0) {
                $term = get_term_by("id", $term->parent, "product_cat");
            }
            $cat_obj = get_term($term->term_id, \'product_cat\');
            $cat_name = $cat_obj->name;
        }
    }
echo \'<br />(\'. $cat_name . \')\';

 $archive_cats= get_terms( \'archivecat\', \'orderby=count&hide_empty=0&parent=0\' );

在本演示中，我们假设我们有一个名为；书籍；。我们可能有一个层次结构：

Fiction (id: 699)
 - This is a Fiction Story.
Non-Fiction
 - Title of Non-fiction
Fantasy
  -  ...

/* Get the Parent Taxonomy Term Name by post Id */

function get_parent_term_by_post_id($taxname, $taxid=null){

if(isset($taxid)):

    //Get by term Id passed in function
    $parent_tax = get_term_by(\'id\', $taxid, $taxname);

    return $parent_tax ->name; //use name, slug, or id

else:

     //Get by PostId of current page
     $terms = wp_get_post_terms( get_the_id(), $taxname);

     $tax_parent_id = $terms[0]->parent;

     if($tax_parent_id == 0):
      $tax_parent_id = $terms[0]->parent; //get the next parent ID
     endif; 

     $parent_tax = get_term_by(\'id\', $tax_parent_id , $taxname);

     return $parent_tax ->name; //use name, slug, or id

endif;

}

//enter custom tax name. will grab by post id 
echo get_parent_term_name_by_post_id(\'books\'); //returns Fiction

//by term ID 
echo get_parent_term_name_by_post_id(\'books\', 699); //returns Fiction