ABSTRACT
The definition of failure and deficiency in mechanical system is reviewed in this research and their relation is discussed. Failure is considered here as a relevant term and not always inability to function as defined and agreed by the companies and stakeholders first. Deficiency is defined as falling short or adverse condition, deterioration, or decay and considered as the potential state or index of a failure. A perceived degradation is an indication that failure will finally occur depending on the failure criterion. A clear failure criterion is needed to relate the deficiency to the failure. A literature review is conducted to evaluate these definitions and their classification in different disciplines and researches. Also, various influential factors as environment, production reputation, natural degradation (ageing) and external stress, which intensify the deficiency of system, are studied. The characteristics of proposed factors are analyzed and their importance on system operation is weighted. Using such weights, the failure intensity index, which reflects the system state, is determined. Through comparing this index with failure criterion, which is specified before, the system failure can be analyzed. So it is concluded that deficiency is just one of the influential factors on system failure while a valid criterion for failure must include all effective factors. Eventually, an application is provided to demonstrate the relation on deficient fire protection
