The variety of complex terms used in the Quality Assurance aspect of analytical measurement can be the cause of considerable confusion. This handbook explains the most widely-used terminology, and attempts to place each term in context. Concepts are described, particularly those concerned with quality assurance, validation and reliability of analytical measurements. Explanations of terms are always in line with the "official definition", often developed by international committees. Adopting a thematic approach, the work is divided into six main parts. The first four parts address the logical progression of an analytical measurement, from obtaining a sample, through method and materials, to reporting the result. The two remaining parts include a variety of terms encountered in quality systems and documentation, along with definitions of "mathematical" terms likely to be encountered by analysts in their everyday work.