In: Advanced Math
definitions of weak topology and weak star topology with as little jargon as possible.
Let 
be a non empty set and 
 be a family of topological spaces. Let 
. Then we define weak topology 
 on 
 in such a way that
each 
 is continuous with respect to 
 in the following
way:
Since we expect each 
 to be
continuous with respect to 
, if 
, then 
. For 
 to be a topology,
it should be closed under arbitrary unions. Let 
, then the topology generated by 
 is the required
topology, i.e., 
 is the basis of the
weak topology 
 generated by
.
Let 
be a normed space and 
 be its dual space.
For each 
, the
functional 
, 
is a semi-norm on 
. The topology
induced by the family of seminorms 
 is the weak topology on 
. Thus, weak star
topology is nothing but the weak topology generated on the dual
space 
 by the family of
functions 
 which will
be continuous in this topology.
The aim to define this kind of topologies is to simplify our study of the space of continuous functions because every function on the topological space (with weak topology) is continuous.