Group theory

A  branchof mathematics that studies the properties of groups, which are algebraicstructures consisting of a set of elements and an operation that combines anytwo elements to form a third one.  Group theory is a central feature of abstractalgebra, and finds applications in a wide variety of fields, includingphysics.  Piaget believed that aschildren construct structures of connected cognitive operations such asaddition or subtraction, based on their experiences and actions, they areconstructing structures that can be studied from the viewpoint of group theory. 

See Bourbaki, Cognitive development, Cognitive structures, Iterative cycle of construction, Network theory, Structure d’esemble