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A second-level domain is the next highest level of the domain name hierarchy after the top-level domain. In a domain name, it is the alphanumeric string immediately to the left of the top-level domain, separated from it by a dot. Second level domain names are often the name of the organization which owns the domain name, e.g.,


Second-level domain names, the name just to the left of ‘.com’, must be exclusive. Therefore, although two companies can have non-exclusive trademark rights in a name, only one company can have a second-level domain name that corresponds to its trademark. * * * In short, the exclusive quality of second-level domain names has set trademark owners against each other in the struggle to establish a commercial presence on the Internet, and has set businesses against domain name holders who seek to continue the traditional use of the Internet as a non-commercial medium of communication.[1]

"Some specific 'vulgar' words and a few words that are prevented by federal statute from being used by private entities are not available as SLDs."[2]

There are several million enterprise-level (second-level or lower) domains. In fact, as of December 2008 there were more than 77 million registered domain names in the .com gTLD alone.


  1. Lockheed Martin Corp. v. Network Solutions, Inc., 985 F. Supp. 949, 952-53, 44 U.S.P.Q.2d (BNA) 1865 (C.D. Cal. 1997) (full-text).
  2. Avery Dennison Corp. v. Sumpton, 189 F.3d 868, 872, 51 U.S.P.Q.2d (BNA) 1801 (9th Cir. 1999) (full-text).