An increasing number of accuracy studies on 3D digitizing systems, especially intraoral scanning devices, are being published in scientific and educational journals. The methods, measurement values, and statistical parameters of these studies vary. Certain inconsistencies exist, which lead to difficulty in terms of interpretation and sometimes even questionable conclusions being drawn. These issues make it almost impossible to compare the results of such studies. One aspect inherent in this is the mutable use of basic terms describing the quality of measurement outcomes. A clear definition of such terms and clear instructions as to their respective calculation processes is essential for communication among scientists as well as for reporting measurement results to the dental community. Therefore, the aim of the present guideline is to provide a clear definition of the accuracy, trueness, and precision as the basic terms in the context of digital dentistry. The survey for this guideline included the application of ISO Norms and their expansion to special aspects concerning 3D data acquisition and, in particular, surface meshes. Additionally, the literature was screened to collect approaches, which can be seen as useful for dealing with these terms when performing different kinds of studies. Keywords: intraoral scanning, accuracy, precision, trueness, ISO standard, 3D evaluation