WordPress Taxonomy

A taxonomy in WordPress is a way to group related content together. It provides a structured method for organizing posts, pages, or custom post types by categories, tags, or custom-defined groups.

Built-in Taxonomies

WordPress includes two default taxonomies for blog posts:

Taxonomy	Description
category	Hierarchical (like folders)
post_tag	Non-hierarchical (like keywords)

Custom Taxonomies

You can define your own taxonomies to organize custom post types more effectively.

Example: Registering a Custom Taxonomy

function create_book_taxonomy() {
    register_taxonomy('genre', 'book', [
        'label' => 'Genres',
        'hierarchical' => true,
        'rewrite' => ['slug' => 'genre'],
        'show_ui' => true,
    ]);
}
add_action('init', 'create_book_taxonomy');

In this example, genre is a custom taxonomy attached to a book post type.

Hierarchical vs Non-Hierarchical

Type	Example	Behavior
Hierarchical	Categories, Genres	Parent-child relationships
Non-hierarchical	Tags, Skills, Keywords	Flat structure

How Taxonomies Work with CPTs

• You can assign multiple taxonomies to a post type.
• Custom taxonomies appear in the WordPress admin like categories or tags.
• They integrate with query tools like WP_Query, tax_query, and template tags.

Displaying Taxonomies

• Template tags: phpCopyEditthe_terms( get_the_ID(), 'genre' );
• Custom archive templates:
  Create taxonomy-genre.php to control how genre pages look.

Querying Posts by Taxonomy

$args = [
    'post_type' => 'book',
    'tax_query' => [
        [
            'taxonomy' => 'genre',
            'field' => 'slug',
            'terms' => 'science-fiction',
        ],
    ],
];
$query = new WP_Query($args);

Summary

Feature	Description
Purpose	Group and organize content
Built-in	category, post_tag
Custom Examples	genre, location, skill
Structure Options	Hierarchical or non-hierarchical
Used With	Posts, Pages, or Custom Post Types