Fault (technology)

In document ISO 10303-226, a fault is defined as an abnormal condition or defect at the component, equipment, or sub-system level which may lead to a failure.
In telecommunications, according to the Federal Standard 1037C of the United States, the term "fault" has the following meanings: 
Random fault.
A random fault is a fault that occurs as a result of wear or other deterioration. Whereas the time of a particular occurrence of such a fault cannot be determined, the rate at which such faults occur within the equipment population on average can be predicted with accuracy. Manufacturers will often accept random faults as a risk if the chances are virtually negligible.
A fault can happen in virtually any object or appliance, most common with electronics and machinery.
For example, an Xbox 360 console will deteriorate over time due to dust buildup in the fans. This will cause the Xbox to overheat, cause an error, and shut the console down.
Systematic fault.
Systematic faults are often a result of an error in the specification of the equipment and therefore affect all examples of that type. Such faults can remain undetected for years, until conditions conduce to create the failure. Given the same circumstances, each and every example of the equipment would fail identically at that time.
Failures in hardware can be caused by random faults or systematic faults, but failures in software are always systematic.