diff --git a/core/lib/Drupal/Core/Routing/routing.api.php b/core/lib/Drupal/Core/Routing/routing.api.php
index 7c5e80a..8b343db 100644
--- a/core/lib/Drupal/Core/Routing/routing.api.php
+++ b/core/lib/Drupal/Core/Routing/routing.api.php
@@ -43,7 +43,7 @@
  *   by the machine name of the module that defines the route, or the name of
  *   a subsystem.
  * - The 'path' line gives the URL path of the route (relative to the site's
- *   base URL).
+ *   base URL). URL path needs to be unique and case-insensitive.
  * - The 'defaults' section tells how to build the main content of the route,
  *   and can also give other information, such as the page title and additional
  *   arguments for the route controller method. There are several possibilities
diff --git a/core/modules/path/path.module b/core/modules/path/path.module
index 307a08b..26a9170 100644
--- a/core/modules/path/path.module
+++ b/core/modules/path/path.module
@@ -20,13 +20,13 @@ function path_help($route_name, RouteMatchInterface $route_match) {
     case 'help.page.path':
       $output = '';
       $output .= '<h3>' . t('About') . '</h3>';
-      $output .= '<p>' . t('The Path module allows you to specify an alias, or custom URL, for any existing internal system path. Aliases should not be confused with URL redirects, which allow you to forward a changed or inactive URL to a new URL. In addition to making URLs more readable, aliases also help search engines index content more effectively. Multiple aliases may be used for a single internal system path. To automate the aliasing of paths, you can install the contributed module <a href=":pathauto">Pathauto</a>. For more information, see the <a href=":path">online documentation for the Path module</a>.', array(':path' => 'https://www.drupal.org/documentation/modules/path', ':pathauto' => 'https://www.drupal.org/project/pathauto')) . '</p>';
+      $output .= '<p>' . t('The Path module allows you to specify an unique and case-insensitive alias, or custom URL, for any existing internal system path. Aliases should not be confused with URL redirects, which allow you to forward a changed or inactive URL to a new URL. In addition to making URLs more readable, aliases also help search engines index content more effectively. Multiple aliases may be used for a single internal system path. To automate the aliasing of paths, you can install the contributed module <a href=":pathauto">Pathauto</a>. For more information, see the <a href=":path">online documentation for the Path module</a>.', array(':path' => 'https://www.drupal.org/documentation/modules/path', ':pathauto' => 'https://www.drupal.org/project/pathauto')) . '</p>';
       $output .= '<h3>' . t('Uses') . '</h3>';
       $output .= '<dl>';
       $output .= '<dt>' . t('Creating aliases') . '</dt>';
-      $output .= '<dd>' . t('If you create or edit a taxonomy term you can add an alias (for example <em>music/jazz</em>) in the field "URL alias". When creating or editing content you can add an alias (for example <em>about-us/team</em>) under the section "URL path settings" in the field "URL alias". Aliases for any other path can be added through the page <a href=":aliases">URL aliases</a>. To add aliases a user needs the permission <a href=":permissions">Create and edit URL aliases</a>.', array(':aliases' => \Drupal::url('path.admin_overview'), ':permissions' => \Drupal::url('user.admin_permissions', array(), array('fragment' => 'module-path')))) . '</dd>';
+      $output .= '<dd>' . t('If you create or edit a taxonomy term you can add an unique and case-insensitive alias (for example <em>music/jazz</em>) in the field "URL alias". When creating or editing content you can add an alias (for example <em>about-us/team</em>) under the section "URL path settings" in the field "URL alias". Aliases for any other path can be added through the page <a href=":aliases">URL aliases</a>. To add aliases a user needs the permission <a href=":permissions">Create and edit URL aliases</a>.', array(':aliases' => \Drupal::url('path.admin_overview'), ':permissions' => \Drupal::url('user.admin_permissions', array(), array('fragment' => 'module-path')))) . '</dd>';
       $output .= '<dt>' . t('Managing aliases') . '</dt>';
-      $output .= '<dd>' . t('The Path module provides a way to search and view a <a href=":aliases">list of all aliases</a> that are in use on your website. Aliases can be added, edited and deleted through this list.', array(':aliases' => \Drupal::url('path.admin_overview'))) . '</dd>';
+      $output .= '<dd>' . t('The Path module provides a way to search and view a <a href=":aliases">list of all aliases</a> that are in use on your website. Aliases need to be unique and case-insensitive. Aliases can be added, edited and deleted through this list.', array(':aliases' => \Drupal::url('path.admin_overview'))) . '</dd>';
       $output .= '</dl>';
       return $output;