In this paper we have investigated enumeration orders of elements of r.e. sets enumerated by means of Turing machines. We have defined a reducibility based on enumeration orders named "Enumeration Order Reducibility" on computable functions and also r.e. sets and studied their properties. Based on this reducibility we introduce an equivalence relation "Enumeration Order Equivalency". We have reached some properties of it. In subsequent, we have introduced another concept named "type-2 Enumeration Order Equivalency" and studied its properties too.