diff --git a/core/lib/Drupal/Core/Entity/Field/FieldItemBase.php b/core/lib/Drupal/Core/Entity/Field/FieldItemBase.php
index 1f264d3..d2c4ad6 100644
--- a/core/lib/Drupal/Core/Entity/Field/FieldItemBase.php
+++ b/core/lib/Drupal/Core/Entity/Field/FieldItemBase.php
@@ -25,7 +25,7 @@
  * Available settings (below the definition's 'settings' key) are:
  *   - property {NAME}: An array containing definition overrides for the
  *     property with the name {NAME}. For example, this can be used by a
- *     computed field to easily override 'class' key of single field value
+ *     computed field to easily override the 'class' key of single field value
  *     only.
  *
  * @see \Drupal\Core\Entity\Field\FieldItemInterface
diff --git a/core/lib/Drupal/Core/Entity/Field/Type/BooleanItem.php b/core/lib/Drupal/Core/Entity/Field/Type/BooleanItem.php
index d10a183..af0652a 100644
--- a/core/lib/Drupal/Core/Entity/Field/Type/BooleanItem.php
+++ b/core/lib/Drupal/Core/Entity/Field/Type/BooleanItem.php
@@ -15,7 +15,7 @@
  * Available settings (below the definition's 'settings' key) are:
  *   - property {NAME}: An array containing definition overrides for the
  *     property with the name {NAME}. For example, this can be used by a
- *     computed field to easily override 'class' key of single field value
+ *     computed field to easily override the 'class' key of single field value
  *     only.
  */
 class BooleanItem extends FieldItemBase {
diff --git a/core/lib/Drupal/Core/Entity/Field/Type/DateItem.php b/core/lib/Drupal/Core/Entity/Field/Type/DateItem.php
index 5f42967..5201051 100644
--- a/core/lib/Drupal/Core/Entity/Field/Type/DateItem.php
+++ b/core/lib/Drupal/Core/Entity/Field/Type/DateItem.php
@@ -15,7 +15,7 @@
  * Available settings (below the definition's 'settings' key) are:
  *   - property {NAME}: An array containing definition overrides for the
  *     property with the name {NAME}. For example, this can be used by a
- *     computed field to easily override 'class' key of single field value
+ *     computed field to easily override the 'class' key of single field value
  *     only.
  */
 class DateItem extends FieldItemBase {
diff --git a/core/lib/Drupal/Core/Entity/Field/Type/EntityReferenceItem.php b/core/lib/Drupal/Core/Entity/Field/Type/EntityReferenceItem.php
index 2ab6367..411aad1 100644
--- a/core/lib/Drupal/Core/Entity/Field/Type/EntityReferenceItem.php
+++ b/core/lib/Drupal/Core/Entity/Field/Type/EntityReferenceItem.php
@@ -17,7 +17,7 @@
  *   - entity type: (required) The entity type to reference.
  *   - property {NAME}: An array containing definition overrides for the
  *     property with the name {NAME}. For example, this can be used by a
- *     computed field to easily override 'class' key of single field value
+ *     computed field to easily override the 'class' key of single field value
  *     only.
  */
 class EntityReferenceItem extends FieldItemBase {
diff --git a/core/lib/Drupal/Core/Entity/Field/Type/IntegerItem.php b/core/lib/Drupal/Core/Entity/Field/Type/IntegerItem.php
index 3a82db9..fc542f1 100644
--- a/core/lib/Drupal/Core/Entity/Field/Type/IntegerItem.php
+++ b/core/lib/Drupal/Core/Entity/Field/Type/IntegerItem.php
@@ -15,7 +15,7 @@
  * Available settings (below the definition's 'settings' key) are:
  *   - property {NAME}: An array containing definition overrides for the
  *     property with the name {NAME}. For example, this can be used by a
- *     computed field to easily override 'class' key of single field value
+ *     computed field to easily override the 'class' key of single field value
  *     only.
  */
 class IntegerItem extends FieldItemBase {
diff --git a/core/lib/Drupal/Core/Entity/Field/Type/LanguageItem.php b/core/lib/Drupal/Core/Entity/Field/Type/LanguageItem.php
index cb230a5..646718b 100644
--- a/core/lib/Drupal/Core/Entity/Field/Type/LanguageItem.php
+++ b/core/lib/Drupal/Core/Entity/Field/Type/LanguageItem.php
@@ -16,7 +16,7 @@
  * Available settings (below the definition's 'settings' key) are:
  *   - property {NAME}: An array containing definition overrides for the
  *     property with the name {NAME}. For example, this can be used by a
- *     computed field to easily override 'class' key of single field value
+ *     computed field to easily override the 'class' key of single field value
  *     only.
  */
 class LanguageItem extends FieldItemBase {
diff --git a/core/lib/Drupal/Core/Entity/Field/Type/StringItem.php b/core/lib/Drupal/Core/Entity/Field/Type/StringItem.php
index 4307d63..85fd6d6 100644
--- a/core/lib/Drupal/Core/Entity/Field/Type/StringItem.php
+++ b/core/lib/Drupal/Core/Entity/Field/Type/StringItem.php
@@ -15,7 +15,7 @@
  * Available settings (below the definition's 'settings' key) are:
  *   - property {NAME}: An array containing definition overrides for the
  *     property with the name {NAME}. For example, this can be used by a
- *     computed field to easily override 'class' key of single field value
+ *     computed field to easily override the 'class' key of single field value
  *     only.
  */
 class StringItem extends FieldItemBase {
diff --git a/core/modules/field/modules/text/lib/Drupal/text/Type/TextItem.php b/core/modules/field/modules/text/lib/Drupal/text/Type/TextItem.php
index 07ae7f9..98b6bb6 100644
--- a/core/modules/field/modules/text/lib/Drupal/text/Type/TextItem.php
+++ b/core/modules/field/modules/text/lib/Drupal/text/Type/TextItem.php
@@ -10,7 +10,13 @@
 use Drupal\Core\Entity\Field\FieldItemBase;
 
 /**
- * Defines the 'text_item' and 'text_long_item' entity field items.
+ * Defines the 'text_field' and 'text_long_field' entity field items.
+ *
+ * Available settings (below the definition's 'settings' key) are:
+ *   - property {NAME}: An array containing definition overrides for the
+ *     property with the name {NAME}. For example, this can be used by a
+ *     computed field to easily override the 'class' key of single field value
+ *     only.
  */
 class TextItem extends FieldItemBase {
 
diff --git a/core/modules/field/modules/text/lib/Drupal/text/Type/TextSummaryItem.php b/core/modules/field/modules/text/lib/Drupal/text/Type/TextSummaryItem.php
index b6438ff..eb563ce 100644
--- a/core/modules/field/modules/text/lib/Drupal/text/Type/TextSummaryItem.php
+++ b/core/modules/field/modules/text/lib/Drupal/text/Type/TextSummaryItem.php
@@ -8,7 +8,13 @@
 namespace Drupal\text\Type;
 
 /**
- * Defines the 'text_with_summary' entity field item.
+ * Defines the 'text_with_summary_field' entity field item.
+ *
+ * Available settings (below the definition's 'settings' key) are:
+ *   - property {NAME}: An array containing definition overrides for the
+ *     property with the name {NAME}. For example, this can be used by a
+ *     computed field to easily override the 'class' key of single field value
+ *     only.
  */
 class TextSummaryItem extends TextItem {