This article does not cite any references or sources. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (December 2009)

In the Domain Name System (DNS) hierarchy, a second-level domain (SLD) is a domain that is directly below a top-level domain (TLD). For example, in example.com, example is the second-level domain of the .com TLD.

Second-level domains commonly refer to the organization that registered the domain name with a domain name registrar. Some domain name registries introduce a second-level hierarchy to a TLD that indicates the type of organization intended to register an SLD under it. For example, in the .uk namespace a college or other academic institution would register under the .ac.uk ccSLD, while companies would register under .co.uk.

[edit] See also

• Country code second-level domain
• Single-letter second-level domains
• Domain Name System
• Top-level domain
• Country code top-level domain
• Subdomain (including "third-level domain" etcetera)