Single-letter second-level domains are domains in which the second-level domain of the domain name consists of only one letter, such as x.com. In 1993, the Internet Assigned Numbers Authority (IANA) explicitly reserved all single-letter and single-digit second-level domains under the top-level domains com, net, and org, and grandfathered those that had already been assigned. In December 2005, ICANN considered auctioning these domain names.