The acquisition, analysis, and comparison of data relating to the “reliability” of nondestructive evaluation (NDE) processes or systems is frequently obscured by a lack of clarity about exactly what is meant by reliability. Different industries make varied use of the term. Even within a single industry, such as aerospace, there is rarely any agreement on the definition of reliability, or of related terms such as capability, repeatability, etc. A set of five defined terms, initially suggested a decade ago, is here revived in the hope that their wider use may help to reduce the confusion. They may form a useful input to a sorely needed national or international standard on NDE reliability terminology.