anchor.diff:    <a href="http://ionicframework.com/" target="_blank">Ionic</a>,
     <a href="https://github.com/angular/angularfire2" target="_blank">AngularFire2</a>).
   
  -  很多Angular库都是模块，比如：`FormsModule`、`HttpModule`、`RouterModule`。
  -  很多第三方库也封装成了Angular模块，比如：<a href="https://material.angular.io/" target="_blank">Material Design</a>、
  -    <a href="http://ionicframework.com/" target="_blank">Ionic</a>、
  -    <a href="https://github.com/angular/angularfire2" target="_blank">AngularFire2</a>。
  +  很多 Angular 库都是模块，例如：`FormsModule`、`HttpModule`、`RouterModule`。
  +  很多第三方库也封装成了 Angular 模块，例如：<a href="https://material.angular.io/" target="_blank">Material Design</a>、
  +  <a href="http://ionicframework.com/" target="_blank">Ionic</a>、
  +  <a href="https://github.com/angular/angularfire2" target="_blank">AngularFire2</a>。
   
     Angular modules consolidate components, directives and pipes into
     cohesive blocks of functionality, each focused on a
     feature area, application business domain, workflow, or common collection of utilities.
   
  -  Angular模块把组件、指令和管道打包成内聚的功能块，每块聚焦于一个特性分区、业务领域、工作流，或一组通用的工具。
  +  Angular 模块把组件、指令和管道打包成内聚的功能块，每个模块聚焦于一个特性区域、业务领域、工作流或通用工具。
   
     Modules can also add services to the application.
     Such services might be internally-developed such as the application logger.
     They can come from outside sources such as the Angular router and Http client.
   
  -  模块还能用来把服务加到应用程序中。这些服务可能是内部研发的，比如应用日志服务；也可能是外部资源，比如Angular路由和Http客户端。
  +  模块还能用来把服务加到应用程序中。这些服务可能是内部研发的，例如应用日志服务；
  +  也可能是外部资源，例如 Angular 路由和 Http 客户端。
   
     Modules can be loaded eagerly when the application starts.
     They can also be _lazy loaded_ asynchronously by the router.
  
positive.code:     deliver different `import` values to root and feature modules.
      Angular doesn't recognize them but Angular developers do.
  
      当需要为根模块和特性模块分别提供不同的`import`值时，***forRoot***和***forChild***也可以作为约定俗成的方法名。
      虽然Angular无法识别它们，但是Angular开发人员可以。
  
      [Follow this convention](../cookbook/ngmodule-faq.html#q-for-root) if you write a similar module
      that has both shared [_declarables_](../cookbook/ngmodule-faq.html#q-declarable) and services.
  
negative.code:     We're importing some extra symbols from the Angular core library that we're not using yet.
      They'll become relevant later in this page.
  
      我们正在从 Angular 核心库中导入一些从未用到的符号，稍后我们会接触它们。
  
  :marked
    The `@NgModule` metadata should be familiar.
  