Creating a form using a path argument
You need to introduce the argument as a 'wildcard', and pass it through to your function in the page arguments like so:

$items['subscribe/verify/%'] = array(
  'title' =&gt; 'Verify Email',
  'page callback' =&gt; 'drupal_get_form',
  'page arguments' =&gt; array('subscribe_terms_form_verify', 2),
  'access arguments' =&gt; array('access content'),
);


The hook_menu() docs are worth read, they explain wildcards in good detail.

Your form function will have this signature:

function subscribe_terms_form_verify($form, &amp;$form_state, $unique_id) {

}


$form and $form_state are provided as parameters to your form through drupal_get_form(), so the 3rd argument will contain the information passed from the URL.