Alter a path alias depending on a node property
if you don't won’t to create a new token as @Clive mentioned in comment, you can use hook_pathauto_alias_alter in your custom module like the following.

/**
 * Implements hook_pathauto_alias_alter().
 */
function MY_MODULE_pathauto_alias_alter(&amp;$alias, array &amp;$context) {
  if ($context['module'] === 'node' &amp;&amp; $context['bundle'] === 'MY_BUNDLE') {
    // Get the node.
    $node = $context['data']['node'];

    // Clean string service.
    $clean_string_service = \Drupal::service('pathauto.alias_cleaner');

    $is_checked = $node-&gt;field_SOME_NAME-&gt;value;
    //   If your field is checked.
    if ($is_checked === 1) {
      $alias = '/mysite/term/' . $clean_string_service-&gt;cleanString($node-&gt;label());
    }
    else {
      $alias = '/mysite/' . $clean_string_service-&gt;cleanString($node-&gt;label());
    }
  }
}