Are Angularjs services singleton?

In the referenceI read: Lastly, it is important to realize that all Angular services are application singletons. This means that there is only one instance of a given service per injector. but with this simple code seems not to be a singleton ``` 'use strict'; angular.module('animal', []) .factory('Animal',function(){ return function(vocalization){ return { vocalization:vocalization, vocalize : function () { console.log('vocalize: ' + this.vocalization); } } } }); angular.module('app', ['animal']) .factory('Dog', function (Animal) { return Animal('bark bark!'); }) .factory('Cat', function (Animal) { return Animal('meeeooooow'); }) .controller('MainCtrl',function($scope,Cat,Dog){ $scope.cat = Cat; $scope.dog = Dog; console.log($scope.cat); console.log($scope.dog); //$scope.cat = Cat; }); ``` I'm a little confused can you explain me what's the matter ? UPDATE 1 May be I'm not the sharpest tool in the shed but afer the @Khanh TO reply it would be a better explanation in the reference it's not very clear. UPDATE 2 ``` 'use strict'; angular.module('animal', []) .factory('Animal',function(){ return { vocalization:'', vocalize : function () { console.log('vocalize: ' + this.vocalization); } } }); angular.module('dog', ['animal']) .factory('Dog', function (Animal) { Animal.vocalization = 'bark bark!'; Animal.color = 'red'; return Animal; }); angular.module('cat', ['animal']) .factory('Cat', function (Animal) { Animal.vocalization = 'meowwww'; Animal.color = 'white'; return Animal; }); angular.module('app', ['dog','cat']) .controller('MainCtrl',function($scope,Cat,Dog){ $scope.cat = Cat; $scope.dog = Dog; console.log($scope.cat); console.log($scope.dog); //$scope.cat = Cat; }); ``` BOOM it's a singleton ! UPDATE 3 But if you do like ``` 'use strict'; angular.module('animal', []) .factory('Animal',function(){ return function(vocalization){ return { vocalization:vocalization, vocalize : function () { console.log('vocalize: ' + this.vocalization); } } } }); angular.module('app', ['animal']) .factory('Dog', function (Animal) { function ngDog(){ this.prop = 'my prop 1'; this.myMethod = function(){ console.log('test 1'); } } return angular.extend(Animal('bark bark!'), new ngDog()); }) .factory('Cat', function (Animal) { function ngCat(){ this.prop = 'my prop 2'; this.myMethod = function(){ console.log('test 2'); } } return angular.extend(Animal('meooow'), new ngCat()); }) .controller('MainCtrl',function($scope,Cat,Dog){ $scope.cat = Cat; $scope.dog = Dog; console.log($scope.cat); console.log($scope.dog); //$scope.cat = Cat; }); ``` it works