clients over their subdomain. Subdomains are also used by organizations that wish to assign a unique name to a particular department, function, or service related to the organization. For example, a university might assign "cs" to the computer science department, such that a number of hosts could be used inside that subdomain, such as www.cs.example.edu. There are some widely recognized subdomains such as WWW and FTP. This allows for a structure where the domain contains administrative directories and files including the FTP directories and webpages. The FTP subdomain could contain logs and the web page directories, while the WWW subdomain contains the directories for the webpages. Independent authentication for each domain provides access control over the various levels of the domain. Uses United Kingdom In the United Kingdom, the second-level domain names are standard and branch off from the top-level domain. For example: .ac.uk - academic (tertiary education, further education colleges and research establishments) and learned societies .co.uk - general use (usually commercial) .gov.uk - government (central and local) .judiciary.uk - courts (to be introduced in the near future) .ltd.uk - limited companies .me.uk - general use (usually personal) .mod.uk - Ministry of Defence and HM Forces public sites .net.uk - ISPs and network companies (unlike .net, use is restricted to these users) .nhs.uk - National Health Service institutions .nic.uk - network use only (Nominet UK) .org.uk - general use (usually for non-profit organisations) .parliament.uk - parliamentary use (only for the UK Parliament and the Scottish Parliament) .plc.uk - public limited companies .police.uk - police forces .sch.uk - Local Education Authorities, schools, primary and secondary education, community education Vanity domain A vanity domain is a subdomain of an ISP's domain that is aliased to an individual user account, or a subdomain that expresses the individuality of the person on whose behalf it is registered. Server cluster Depending on application, a record inside a domain, or subdomain might refer to a hostname, or a service provided by a number of machines in a cluster. Some websites use different subdomains to point to different server clusters. For example, www.example.com points to Server Cluster 1 or Datacentre 1, and www2.example.com points to Server Cluster 2 or Datacentre 2 etc. Subdomains versus directories Subdomains are different from directories. Directories are physical folders on an actual computer, while subdomains are a part of the URL that can be routed to any file or folder on