Answer: Answering this question requires a long and precise discussion; however, we can say in summary that among the Islamic thinkers, the Islamic economics is applied by one of the following concepts;
Economic rules: these are juristic rules around economics. For example, the rules that say "Usury is forbidden" or "wasting is illegal" or "it is necessary to consume things based on the needs" are all around the economic subjects.
Economic principles: economic principles are general issues that can be deduced directly or indirectly from the economic rules. For instance, the following sentence can be regarded as an economic principle, "among the personal and common interests, the latter one has the legal priority'. This principle can be deduced from the rules such wasting prohibition; damage prohibition; distress and constriction prohibition; interest wasting prohibition …
Economic school: the economic school is in fact a collection of economic principles that determine the general orientation of the economic system. In fact, applying the "school" can be a suitable way to solve the economic problems.
Economic system: it is a collection of inter-related elements, which supply a special target in the economic domain. In fact, the economic system includes the economic school plus the special methods and frameworks of each society in each era.
Generally, we can mention that the concept of Islamic economy in Imam's words indicate a coherent collection of Islamic instructions which contain the above four domains, relatively defined and systematic with Islam.