offset question

offset question

  2. var p = $( "p:last" );
  3. var offset = p.offset();
  4. p.html( "left: " + offset.left + ", top: " + offset.top );

the above code works just fine , but why is it that when i change the last line to 

  1. p.html("left: " + offset.right + ", top: " + offset.top );
i get the following output 

left: undefined, top: 52

WHY UNDEFINED , can somebody explain ? Thank u :D