:
All  A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z  Other  
Sub-Domain

A sub-domain is a domain that is part of a larger domain; the only domain that is not also a sub-domain is the root domain. For example, doit.wisc.edu and engr.wisc.edu are sub-domains of the wisc.edu domain.