For Creating Custom Texonomies in Wordpress Have Function
register_taxonomy () Function
Example Code : Below PHP Code Will Create genre texonomy in Wordpress
<?php
add_action( 'init', 'create_book_tax' );
function create_book_tax() {
register_taxonomy(
'genre',
'book',
array(
'label' => __( 'Genre' ),
'rewrite' => array( 'slug' => 'genre' ),
'hierarchical' => true,
)
);
}