Tehran University of Medical Sciences Iranian Journal of Public Health 2251-6085 5 3 1976 09 15 121 142 H. A. Rafatjah 2015 10 03 The term “system” is defined as «elements standing interaction». This implies that a change in any given element should bring about changes in other elements of the system and thus may be used to identify the boundaries of a system. A system can be a machine, a man, or a community. Each of these may be part of a greater system (super system) or include several smaller systems (subsystems). Systems analysis studies the constituent elements of a system and the interactions between them. It will help program planners and managers to understand the functioning of the system, to use comprehensive approach in planning and to discover deficiencies in implementation and find way to solve them. https://ijph.tums.ac.ir/index.php/ijph/article/view/2432 https://ijph.tums.ac.ir/index.php/ijph/article/download/2432/2412