diff -u b/core/modules/field/field.form.inc b/core/modules/field/field.form.inc
--- b/core/modules/field/field.form.inc
+++ b/core/modules/field/field.form.inc
@@ -21,9 +21,9 @@
  */
 function template_preprocess_field_multiple_value_form(&$variables) {
   $element = $variables['element'];
-  $variables['multiple_cardinality'] = $element['#cardinality_multiple'];
+  $variables['multiple'] = $element['#cardinality_multiple'];
 
-  if ($variables['multiple_cardinality']) {
+  if ($variables['multiple']) {
 
     $table_id = drupal_html_id($element['#field_name'] . '_values');
     $order_class = $element['#field_name'] . '-delta-order';
diff -u b/core/modules/field/field.module b/core/modules/field/field.module
--- b/core/modules/field/field.module
+++ b/core/modules/field/field.module
@@ -8,6 +8,7 @@
 use Drupal\Core\Template\Attribute;
 use Drupal\field\FieldInterface;
 use Drupal\field\FieldInstanceInterface;
+use Drupal\Component\Utility\String;
 
 /*
  * Load all public Field API functions. Drupal currently has no
@@ -629,7 +630,7 @@
   $variables['label_hidden'] = ($element['#label_display'] == 'hidden');
   // Always set the field label - allow themes to decide whether to display
   // In addition the label should be rendered but hidden to support screen readers
-  $variables['label'] = check_plain($element['#title']);
+  $variables['label'] = String::checkPlain($element['#title']);
 
   // We want other preprocess functions and the theme implementation to have
   // fast access to the field item render arrays. The item render array keys
diff -u b/core/modules/field/templates/field-multiple-value-form.html.twig b/core/modules/field/templates/field-multiple-value-form.html.twig
--- b/core/modules/field/templates/field-multiple-value-form.html.twig
+++ b/core/modules/field/templates/field-multiple-value-form.html.twig
@@ -4,13 +4,13 @@
  * Default theme implementation for an individual form element.
  *
  * Available variables for all fields:
- * - multiple_cardinality: Whether the field is multiple cardinality or not.
+ * - multiple: Whether there are multiple instances of the field.
  *
  * Available variables for single cardinality fields:
  * - elements: Form elements to be rendered.
  *
- * Available variables for multiple cardinality fields:
- * - table: Table of field items for multiple cardinality fields.
+ * Available variables when there are multiple fields.
+ * - table: Table of field items.
  * - description: Description text for the form element.
  * - button: "Add another item" button.
  *
@@ -19,7 +19,7 @@
  * @ingroup themeable
  */
 #}
-{% if multiple_cardinality %}
+{% if multiple %}
   <div class="form-item">
     {{ table }}
     {% spaceless %}