stderr redirection to stdout

To redirect stderr to stdout we use 2 > &1. Why is it not just 2 > 1? why & is needed?

From stackoverflow

• because your stream would be redirected to file named "1"

  chappar : so, why it is not &2 > &1. :-)

  Benny Wong : because 2 in that case is not ambiguous

• Because 2>1 would redirect to a file named "1". The & symbol specifies a stream rather than a file. The & symbol is not necessary for the 2 because the 2 is always a stream inidcator