The terms used in most engineering technologies tend to be physical characteristics such as speed, rate of turn, and fuel consumption. While they may require very careful definition and control of the way in which they are measured, the terms themselves are not subject to different interpretations. Reliability, maintainability and supportability (RMS) however, use terms that are mathematically defined. As a result, there are more than 2000 terms defined in just the documents reviewed so far, many of which have multiple interpretations. This proliferation of definitions of the terms leads to problems when one attempts to compare the performance of one system to another. For example, the RMS performance of a transport aircraft from the commercial arena is measured using metrics that are not the same as those for a fighter or attack aircraft from a military service.