add_action( 'init', 'work_register' );

function work_register() {

$labels = array(
    'name' => _x('Work', 'post type general name'),
    'singular_name' => _x('Work Item', 'post type singular name'),
    'add_new' => _x('Add New', 'work item'),
    'add_new_item' => __('Add New Work Item'),
    'edit_item' => __('Edit Work Item'),
    'new_item' => __('New Work Item'),

    'view_item' => __('View Work Item'),
    'search_items' => __('Search Work'),
    'not_found' => __('Nothing found'),
    'not_found_in_trash' => __('Nothing found in Trash'),
    'parent_item_colon' => ''
);

$args = array(
    'labels' => $labels,
    'public' => true,
    'publicly_queryable' => true,
    'show_ui' => true,
    'query_var' => true,
    'menu_icon' => get_stylesheet_directory_uri() . '/article16.png',
    'rewrite' => array( 'slug' => 'work', 'with_front'=> false ),
    'capability_type' => 'post',
    'hierarchical' => true,
    'has_archive' => true,
    'menu_position' => null,
    'supports' => array('title','editor','thumbnail')
);

register_post_type( 'work' , $args );

register_taxonomy( 'categories', array('work'), array(
    'hierarchical' => true,
    'label' => 'Categories',
    'singular_label' => 'Category',
    'rewrite' => array( 'slug' => 'categories', 'with_front'=> false )
    )
);

register_taxonomy_for_object_type( 'categories', 'work' );

/%category%/%postname%/

/category/postname

/postname