--- a/core/modules/system/src/Controller/SystemController.php
+++ b/core/modules/system/src/Controller/SystemController.php
@@ -312,7 +307,7 @@
         $theme->notes[] = $this->t('default theme');
       }
       if ($theme->is_admin) {
-        $theme->notes[] = $this->t('admin theme');
+        $theme->notes[] = $this->t('administration theme');
       }
 
       // Sort installed and uninstalled themes into their own groups.