Seidel switching is often called simply switching. Switching with respect to a subset 
of the vertex set 
of a simple graph 
produces a graph on 
by changing every edge between 
and 
to a non-edge and every non-edge between the two sets to
an edge. Edges having both endpoints in 
or both in 
are unchanged (Seidel 1974).
Switching with respect to 
gives the same graph as switching with respect to 
, and applying the same switch twice returns 
. Two graphs on the same vertex set are switching equivalent
if one can be obtained from the other by Seidel switching. The resulting equivalence
classes are known as switching classes.
