Fault
failure to reach or maintain a measured standard of reliability or performance. With respect to condition monitoring, additional terms relating to fault are:
| Occurrence | Any detected or diagnosed fault requiring remedial action whether the action was reactive, preventive or proactive |
| Apparent Fault Condition | A diagnostic system reading indicates an abnormal condition, pending confirmation and evaluation of severity |
| True Fault Condition | An apparent fault condition has been confirmed as a valid abnormal condition (by inspection, multi-technique cross checking, loss or variance in performance, etc.) |
| False Alarm | An apparent fault condition has not been confirmed or has been traced to an external cause (sampling or instrument error, misidentification, judgement error, etc.) |