diff --git a/core/misc/cspell/dictionary.txt b/core/misc/cspell/dictionary.txt
index 6c166b2aafa619694fa88b933b7adf7f5f0cb538..2e3478932ac2237965f08f66ca968d563798d011 100644
--- a/core/misc/cspell/dictionary.txt
+++ b/core/misc/cspell/dictionary.txt
@@ -581,7 +581,6 @@ evenodd
 eventhandler
 exampleurl
 exdep
-existant
 exitcode
 expirable
 extlink
diff --git a/core/modules/migrate/tests/src/Unit/RowTest.php b/core/modules/migrate/tests/src/Unit/RowTest.php
index 4161900784d2ba9f50a430a587d49f6c1a0d62d9..8392220c6a69e36074fe2834f12a5676ee1d145c 100644
--- a/core/modules/migrate/tests/src/Unit/RowTest.php
+++ b/core/modules/migrate/tests/src/Unit/RowTest.php
@@ -405,15 +405,15 @@ public function getMultipleDataProvider() {
           'destination_value_3',
         ],
       ],
-      'Mix of keys including non-existant' => [
+      'Mix of keys including non-existent' => [
         'keys' => [
           'shared_key_1',
           '@shared_key_1',
           '@@shared_key_2',
           '@@@shared_key_2',
           '@@@@@@@@@shared_key_3',
-          'non_existant_source_key',
-          '@non_existant_destination_key',
+          'non_existent_source_key',
+          '@non_existent_destination_key',
         ],
         'values' => [
           'source_shared_value_1',
diff --git a/core/tests/Drupal/Tests/Component/DependencyInjection/ContainerTest.php b/core/tests/Drupal/Tests/Component/DependencyInjection/ContainerTest.php
index 2172f20180d43a7658edcef425a1d2ab0e78369b..516dae38f3bebb60935df6b4e053d4aa0b8cd5da 100644
--- a/core/tests/Drupal/Tests/Component/DependencyInjection/ContainerTest.php
+++ b/core/tests/Drupal/Tests/Component/DependencyInjection/ContainerTest.php
@@ -254,7 +254,7 @@ public function testGetForCircularServices() {
    * @covers ::getAlternatives
    * @covers ::getServiceAlternatives
    */
-  public function testGetForNonExistantService() {
+  public function testGetForNonExistentService() {
     $this->expectException(ServiceNotFoundException::class);
     $this->container->get('service_not_exists');
   }
@@ -286,7 +286,7 @@ public function testGetForSerializedServiceDefinition() {
    * @covers ::createService
    * @covers ::resolveServicesAndParameters
    */
-  public function testGetForNonExistantParameterDependency() {
+  public function testGetForNonExistentParameterDependency() {
     $service = $this->container->get('service_parameter_not_exists', ContainerInterface::NULL_ON_INVALID_REFERENCE);
     $this->assertNull($service, 'Service is NULL.');
   }
@@ -315,7 +315,7 @@ public function testGetForParameterDependencyWithExceptionOnSecondCall() {
    * @covers ::createService
    * @covers ::resolveServicesAndParameters
    */
-  public function testGetForNonExistantParameterDependencyWithException() {
+  public function testGetForNonExistentParameterDependencyWithException() {
     $this->expectException(InvalidArgumentException::class);
     $this->container->get('service_parameter_not_exists');
   }
@@ -327,7 +327,7 @@ public function testGetForNonExistantParameterDependencyWithException() {
    * @covers ::createService
    * @covers ::resolveServicesAndParameters
    */
-  public function testGetForNonExistantServiceDependency() {
+  public function testGetForNonExistentServiceDependency() {
     $service = $this->container->get('service_dependency_not_exists', ContainerInterface::NULL_ON_INVALID_REFERENCE);
     $this->assertNull($service, 'Service is NULL.');
   }
@@ -340,7 +340,7 @@ public function testGetForNonExistantServiceDependency() {
    * @covers ::resolveServicesAndParameters
    * @covers ::getAlternatives
    */
-  public function testGetForNonExistantServiceDependencyWithException() {
+  public function testGetForNonExistentServiceDependencyWithException() {
     $this->expectException(ServiceNotFoundException::class);
     $this->container->get('service_dependency_not_exists');
   }
@@ -351,7 +351,7 @@ public function testGetForNonExistantServiceDependencyWithException() {
    * @covers ::get
    * @covers ::createService
    */
-  public function testGetForNonExistantServiceWhenUsingNull() {
+  public function testGetForNonExistentServiceWhenUsingNull() {
     $this->assertNull($this->container->get('service_not_exists', ContainerInterface::NULL_ON_INVALID_REFERENCE), 'Not found service does not throw exception.');
   }
 
@@ -360,7 +360,7 @@ public function testGetForNonExistantServiceWhenUsingNull() {
    * @covers ::get
    * @covers ::createService
    */
-  public function testGetForNonExistantNULLService() {
+  public function testGetForNonExistentNULLService() {
     $this->expectException(ServiceNotFoundException::class);
     $this->container->get(NULL);
   }
@@ -371,7 +371,7 @@ public function testGetForNonExistantNULLService() {
    * @covers ::get
    * @covers ::createService
    */
-  public function testGetForNonExistantServiceMultipleTimes() {
+  public function testGetForNonExistentServiceMultipleTimes() {
     $container = new $this->containerClass();
 
     $this->assertNull($container->get('service_not_exists', ContainerInterface::NULL_ON_INVALID_REFERENCE), 'Not found service does not throw exception.');
@@ -385,7 +385,7 @@ public function testGetForNonExistantServiceMultipleTimes() {
    * @covers ::createService
    * @covers ::getAlternatives
    */
-  public function testGetForNonExistantServiceWithExceptionOnSecondCall() {
+  public function testGetForNonExistentServiceWithExceptionOnSecondCall() {
     $this->assertNull($this->container->get('service_not_exists', ContainerInterface::NULL_ON_INVALID_REFERENCE), 'Not found service does nto throw exception.');
     $this->expectException(ServiceNotFoundException::class);
     $this->container->get('service_not_exists');
diff --git a/core/tests/Drupal/Tests/Core/Plugin/Discovery/HookDiscoveryTest.php b/core/tests/Drupal/Tests/Core/Plugin/Discovery/HookDiscoveryTest.php
index c103b0144198316fabc2da1fad2117f8fc000fc4..f528e5f631fc1db07f7bd915187dd95db1960642 100644
--- a/core/tests/Drupal/Tests/Core/Plugin/Discovery/HookDiscoveryTest.php
+++ b/core/tests/Drupal/Tests/Core/Plugin/Discovery/HookDiscoveryTest.php
@@ -100,7 +100,7 @@ public function testGetDefinition() {
         ]
       ));
 
-    $this->assertNull($this->hookDiscovery->getDefinition('test_non_existant', FALSE));
+    $this->assertNull($this->hookDiscovery->getDefinition('test_non_existent', FALSE));
 
     $plugin_definition = $this->hookDiscovery->getDefinition('test_id_1');
     $this->assertEquals($plugin_definition['class'], 'Drupal\plugin_test\Plugin\plugin_test\fruit\Apple');
@@ -126,7 +126,7 @@ public function testGetDefinitionWithUnknownID() {
       ->will($this->returnValue([]));
 
     $this->expectException(PluginNotFoundException::class);
-    $this->hookDiscovery->getDefinition('test_non_existant', TRUE);
+    $this->hookDiscovery->getDefinition('test_non_existent', TRUE);
   }
 
   protected function hookDiscoveryTestTestPlugin() {