With hundreds of these objects now known, we are discovering details that make Pluto‚Äôs place in the solar system.  We now have a number of three letter acronyms which define different classes of these objects. Most recently, the I.A.U. has decided on the designation 'pluton' for that class of smaller objects similar to Pluto. However, there is still some confusion about the new terms   The largest of these objects, Eris, is in fact bigger than Pluto.
Carpe Caelum Planetary Astronomy