:first-child        :first-of-type        :only-child
:last-child         :last-of-type         :only-of-type                  
:nth-child          :nth-of-type    
:nth-last-child     :nth-last-of-type

::first-letter      ::first-line          ::first-word
::last-letter       ::last-line           ::last-word
::nth-letter        ::nth-line            ::nth-word
::nth-last-letter   ::nth-last-line       ::nth-last-word