diff --git a/change-log.md b/change-log.md
index f28600775..e7ebf0825 100644
--- a/change-log.md
+++ b/change-log.md
@@ -13,6 +13,7 @@ All changes:
 * [#110](https://github.com/mnapoli/PHP-DI/issues/110) XML definitions are not supported anymore
 * [#122](https://github.com/mnapoli/PHP-DI/issues/122) JSON definitions are not supported anymore
 * `ContainerSingleton` has finally been removed
+* `FactoryInterface` has been renamed to `Injector`, only people implementing their own factory/injector should care
 
 ## 3.4
 
diff --git a/doc/how-it-works.md b/doc/how-it-works.md
index 30e32fa15..a5e2152f7 100644
--- a/doc/how-it-works.md
+++ b/doc/how-it-works.md
@@ -17,7 +17,7 @@ $entry = $container->get('entryName');
 A container instance has the following sub-components:
 
 - a `DefinitionManager` that returns a `Definition` for an entry name
-- a `Factory` to create instances from the definitions
+- an `Injector` to create instances from the definitions
 
 ### Definitions
 
@@ -62,6 +62,9 @@ It answers the following needs:
 
 *This could be improved by splitting this into 2 separate classes to follow the [Single Responsibility Principle](http://en.wikipedia.org/wiki/Single_responsibility_principle).*
 
-### Factory
+### Injector
 
-The role of the `Factory` is to return an object instance from a `ClassDefinition`.
+The role of the `Injector` is to process "Definitions".
+
+It can return a new instance (with dependencies injected) from a `ClassDefinition`, or also inject dependencies on an
+existing instance.
diff --git a/src/DI/Container.php b/src/DI/Container.php
index 9720e9ee5..70e8667f1 100644
--- a/src/DI/Container.php
+++ b/src/DI/Container.php
@@ -38,9 +38,9 @@ class Container
     private $definitionManager;
 
     /**
-     * @var FactoryInterface
+     * @var Injector
      */
-    private $factory;
+    private $injector;
 
     /**
      * @var LazyLoadingValueHolderFactory
@@ -58,16 +58,16 @@ class Container
      * Parameters are optional, use them to override a dependency.
      *
      * @param DefinitionManager|null             $definitionManager
-     * @param FactoryInterface|null              $factory
+     * @param Injector|null              $injector
      * @param LazyLoadingValueHolderFactory|null $proxyFactory
      */
     public function __construct(
         DefinitionManager $definitionManager = null,
-        FactoryInterface $factory = null,
+        Injector $injector = null,
         LazyLoadingValueHolderFactory $proxyFactory = null
     ) {
         $this->definitionManager = $definitionManager ?: $this->createDefaultDefinitionManager();
-        $this->factory = $factory ?: $this->createDefaultFactory();
+        $this->injector = $injector ?: $this->createDefaultInjector();
         $this->proxyFactory = $proxyFactory ?: $this->createDefaultProxyFactory();
 
         // Auto-register the container
@@ -161,7 +161,7 @@ public function injectOn($instance)
 
         // Check that the definition is a class definition
         if ($definition instanceof ClassDefinition) {
-            $instance = $this->factory->injectOnInstance($definition, $instance);
+            $instance = $this->injector->injectOnInstance($definition, $instance);
         }
 
         return $instance;
@@ -195,19 +195,19 @@ public function addDefinitions(array $definitions)
     }
 
     /**
-     * @param FactoryInterface $factory
+     * @param Injector $injector
      */
-    public function setFactory(FactoryInterface $factory)
+    public function setInjector(Injector $injector)
     {
-        $this->factory = $factory;
+        $this->injector = $injector;
     }
 
     /**
-     * @return FactoryInterface
+     * @return Injector
      */
-    public function getFactory()
+    public function getInjector()
     {
-        return $this->factory;
+        return $this->injector;
     }
 
     /**
@@ -250,7 +250,7 @@ private function getNewInstance(ClassDefinition $classDefinition)
         $this->classesBeingInstantiated[$classname] = true;
 
         try {
-            $instance = $this->factory->createInstance($classDefinition);
+            $instance = $this->injector->createInstance($classDefinition);
         } catch (Exception $exception) {
             unset($this->classesBeingInstantiated[$classname]);
             throw $exception;
@@ -293,11 +293,11 @@ private function createDefaultDefinitionManager()
     }
 
     /**
-     * @return FactoryInterface
+     * @return Injector
      */
-    private function createDefaultFactory()
+    private function createDefaultInjector()
     {
-        return new Factory($this);
+        return new DefaultInjector($this);
     }
 
     /**
diff --git a/src/DI/Factory.php b/src/DI/DefaultInjector.php
similarity index 96%
rename from src/DI/Factory.php
rename to src/DI/DefaultInjector.php
index 59c3aeec5..3853a9910 100644
--- a/src/DI/Factory.php
+++ b/src/DI/DefaultInjector.php
@@ -23,11 +23,12 @@
 use ReflectionParameter;
 
 /**
- * Factory class, responsible of instantiating classes
+ * Component responsible of creating and injecting dependencies as defined in Definitions.
  *
  * @author Matthieu Napoli <matthieu@mnapoli.fr>
+ * @since 4.0
  */
-class Factory implements FactoryInterface
+class DefaultInjector implements Injector
 {
     /**
      * @var Container
@@ -82,7 +83,7 @@ public function injectOnInstance(ClassDefinition $classDefinition, $instance)
     }
 
     /**
-     * Creates an instance and inject dependencies through the constructor
+     * Creates an instance and inject dependencies through the constructor.
      *
      * @param ReflectionClass      $classReflection
      * @param MethodInjection|null $constructorInjection
@@ -177,7 +178,7 @@ private function prepareMethodParameters(MethodInjection $methodInjection = null
     }
 
     /**
-     * Inject dependencies into properties
+     * Inject dependencies into properties.
      *
      * @param object            $object            Object to inject dependencies into
      * @param PropertyInjection $propertyInjection Property injection definition
@@ -213,9 +214,11 @@ private function injectProperty($object, PropertyInjection $propertyInjection)
     }
 
     /**
-     * Returns the default value of a function parameter
+     * Returns the default value of a function parameter.
+     *
      * @param ReflectionParameter $reflectionParameter
      * @param ReflectionMethod    $reflectionMethod
+     *
      * @throws DefinitionException Can't get default values from PHP internal classes and methods
      * @return mixed
      */
diff --git a/src/DI/FactoryInterface.php b/src/DI/Injector.php
similarity index 59%
rename from src/DI/FactoryInterface.php
rename to src/DI/Injector.php
index ff623469a..6cdb88beb 100644
--- a/src/DI/FactoryInterface.php
+++ b/src/DI/Injector.php
@@ -12,26 +12,29 @@
 use DI\Definition\ClassDefinition;
 
 /**
- * Factory class, responsible of instantiating classes
+ * Component responsible of creating and injecting dependencies as defined in Definitions.
  *
  * @author Matthieu Napoli <matthieu@mnapoli.fr>
+ * @since 4.0
  */
-interface FactoryInterface
+interface Injector
 {
     /**
-     * Create a new instance of the class
+     * Create a new instance of a class and injects all dependencies.
      *
      * @param ClassDefinition $classDefinition
      *
      * @return object The instance
      */
-    function createInstance(ClassDefinition $classDefinition);
+    public function createInstance(ClassDefinition $classDefinition);
 
     /**
+     * Injects dependencies on an existing instance.
+     *
      * @param ClassDefinition $classDefinition
      * @param object          $instance
      *
      * @return object The instance
      */
-    function injectOnInstance(ClassDefinition $classDefinition, $instance);
+    public function injectOnInstance(ClassDefinition $classDefinition, $instance);
 }