WebLogicDomain的定义，翻译出来大家交流，第一次作赏个脸：]

What Is a WebLogic Domain?
什么是WebLogic Domain?
The basic administrative unit for WebLogic Server is a domain.
WebLogic服务器基本管理单元就是一个Domain。
A domain is an interrelated set of WebLogic Server resources that are managed as a unit.
一个domain是一些相关的设置作为一个单元被管理的WebLogic服务器资源。   
A domain includes one or more WebLogic Server instances, and may also include WebLogic Server clusters.
一个domain包括一个或者更多的WebLogic Server实例，也可能包括WebLogic Server集群。
Clusters are groups of WebLogic Servers that work together to provide scalability and high-availability for applications.
集群是工作在一起的提供可靠高效应用的WebLogic Servers组。
One instance of WebLogic Server in each domain is configured as an Administration Server.
每一个domain中的WebLogic Server实例是都是由Administration Server配置的。
The Administration Server provides a central point for managing a WebLogic domain.
Administration Server提供一个管理WebLogic domain的中心点。
All other WebLogic Server instances in a domain are called Managed Servers.
所有其他的WebLogic Server实例在domain中被称为Managed Servers。
In a domain with only a single WebLogic Server instance, that server functions as both Administration Server and Managed Server.
当一个domain仅有一个单一的WebLogic Server实例的时候，这个服务器兼有Administration Server和Managed Server功能。