Theoretical aspects of emergence and development of the crisis phenomena in economy

The article examines genesis of emergence and development of the crisis phenomena in economy of the countries of the world and their research in works of scientists. The main theories explaining the reasons of cyclic crises and chronology of change of views of scientists on recurrence in development of social and economic systems are considered. The essence of the concepts "crisis" and "economic crisis" is defined. Crisis functions in dynamics of development of systems and a crisis stage are considered. As crisis is one of stages of a business cycle, phases of such cycle in economy and main versions of business cycles are considered. Basic clauses of the theory of the crises, which have been formed by the beginning of the XXI century, are specified.