WordPress - Modify default role names “Administrator, Editor, Author, Contributor, Subscriber” to fit your needs

functions.php

/*
Change the default role names (Administrator, Editor, Author, Contributor, Subscriber) to any custom names.
Add the following code in theme's functions.php file (edit lines 5 and 6 for custom name).
*/

function wp_change_role_name() {
    global $wp_roles;
    if ( ! isset( $wp_roles ) )
        $wp_roles = new WP_Roles();
    $wp_roles->roles['contributor']['name'] = 'Owner';
    $wp_roles->role_names['contributor'] = 'Owner';
}
add_action('init', 'wp_change_role_name');