
Topology  Wikipedia, the free encyclopedia 
  Topology has sometimes been called rubbersheet geometry, because it does not distinguish between a circle and a square (a circle made out of a rubber band can be stretched into a square) but does distinguish between a circle and a figure eight (you cannot stretch a figure eight into a circle without tearing). 
  In pointless topology one considers instead the lattice of open sets as the basic notion of the theory, while Grothendieck topologies are certain structures defined on arbitrary categories which allow the definition of sheaves on those categories, and with that the definition of quite general cohomology theories. 
  However, Lacan's use of topology, like his use of algebra, does not meet the standards of rigour normally evinced by a mathematical discipline, and should be seen more as an analogy (the value of which is left to the reader to decide upon) than as a branch of applied mathematics. 
 en.wikipedia.org /wiki/Topology (1876 words) 