register_post_type

$args = array(
 'label' => __('Projets'),
 'singular_label' => __('Projet'),
 'public' => true,
 'show_ui' => true,
 '_builtin' => false,
 '_edit_link' => 'post.php?post=%d',
 'capability_type' => 'post',
 'hierarchical' => false,
 'rewrite' => array("slug" => "projects"),
 'query_var' => "projets",
 'supports' => array('title', 'editor', 'editor', 'editor', 'thumbnail')
);
register_post_type( 'projet' , $args );