Failures are often due to a complex set of stochastic interactions between the loads that act on a product and the various elements (design, materials, components, software, fabrication) that comprise the product. Preventing failures by understanding and improving product quality and reliability is sometimes hindered by the misapplication of important terminology. The intent of this article is to reduce miscommunications by defining some of the key vocabulary used in the field of quality and reliability, and by explaining their misuse and appropriate use.