Example of hook form alter

This is an example for altering form

function helper_form_alter(&$form, &$form_state, $form_id) {   
    //var_dump($form_id);
    switch ($form_id){
        case 'user_profile_form' :
            unset ($form['user_terms']); // remove user_term form
            unset ($form['locale']); //remove locale form
            break;
    }
}