域名DNS相关术语介绍、中英文对照
Registrant（注册人）
The entity that has acquired the right to use an Internet resource. Usually this is via some form of revocable grant given by a registrar to list their registration in a registry.
获得使用互联网资源权利的实体。通常，借助注册服务商提供的某种形式的可撤销授权，在注册管理机构列出其注册来获得使用权。
Registrar（注册商）
An entity that can act on requests from a registrant in making changes in a registry. Usually the registrar is the same entity that operates a registry, although for domain names this role is often split to allow for competition between multiple registrars who offer different levels of support. See also domain name registrar.
一个可以根据注册人提出的变更注册局的申请而采取行动的实体。通常，注册商就是运营注册局的实体，尽管对于域名来说，通常情况下会对这两种角色加以区分，以允许在提供不同支持等级的多个注册商之间形成竞争。请同时参阅”域名注册商”。
Registry（注册局）
The authoritative record of registrations for a particular set of data. Most often used to refer to domain name registry, but all protocol parameters that IANA maintains are also registries.
关于特定数据集注册的权威记录。通常是指域名注册局，但是 IANA 维护的所有协议参数也属于注册局。
Registry Operator（注册局运营商）
The entity that runs a registry.
运营注册局的实体。
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怎样？有点乱，一张图让你看明白：
Top-Level Domain (TLD,顶级域名)
The highest level of subdivisions with the domain name system. These domains, such as “.COM” and “.UK” are delegated from the DNS Root zone. They are generally divided into two distinct categories, generic top-level domains and country-code top-level domains.
域名系统分类中的最高层级。包括”.COM”和”.UK”在内的顶级域名从 DNS 根区域中授权。顶级域名通常分为两个不同的类别：通用顶级域名和国家或地区顶级域名。
Generic Top-Level Domains (gTLDs, 通用顶级域名)
A class of top-level domains that are used for general purposes, where ICANN has a strong role in coordination (as opposed to country-code top-level domains, which are managed locally). For policy reasons, these are usually subdivided into sponsored top-level domains and unsponsored top-level domains.
一类用于通用目的的顶级域名，ICANN 在这些域名中发挥重要的协调作用（与本地管理的”国家和地区代码顶级域名”相对）。基于政策原因，通用顶级域名通常细分为社区性顶级域名和非社区性顶级域名。
Country-code Top-Level Domain (ccTLD, 国家或地区顶级域名)
A class of top-level domains only assignable to represent countries listed in the ISO 3166-1 standard. At present these are two-letter codes like “.UK”, “.DE” etc., however in the future it is expected there will be non-Latin equivalents also available. Much of the policy-making for individual country-code top-level domains is vested with a local sponsoring organization, as opposed to other top-level domains where ICANN sets the policy. It is a requirement that ccTLDs are operated within the country they are designated so appropriate local laws, governments etc. have a say in how the domain is run.
一类只能分配给代表 ISO 3166-1 标准所列出的国家和地区的顶级域名。目前，这类域名是由两个字母组成的代码，例如”.UK”、”.DE”等，预计将来还会提供非拉丁文的同义代码。多数针 对各个国家或地区顶级域名的政策都是授权当地发起组织制定，这与其他由 ICANN 制定政策的顶级域名不同。需要满足的要求是：ccTLD 在指定的国家或地区范围内使用，因此，当地法律和政府部门对域名的运营拥有发言权。
所有的TLD顶级域名都可以从IANA的网站上查到：
http://www.iana.org/domains/root/db
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