On any quiver ô��³and a field ô��, we can define a ô��-algebra which is called a path algebra ô��ô��³. This path algebra has a basis that is the set of all paths in the quiver. Conversely, a finite dimensional algebra ô��£can be obtained by a quiver ô��³ô�®º. Furthermore, a quiver representation â�� = (ô��¸ô�¯� , ô���ô�°�) can be formed on any quiver. A representation of a quiver ô��³is an assignment of a vector space to each vertex and a linear mapping to each arrow. A representation which has no proper subrepresentation except zero is called a simple representation. Furthermore, if ô��¸and ô��¹ are the representations of quiver ô��³, then it can be formed a new representation which is called a direct sum of V and W and denoted by ô��¸â...