The purpose of this article is to clarify the shift to the term "intellectual disability." At the heart of that shift is the understanding that this term covers the same population of individuals who were diagnosed previously with mental retardation in number, kind, level, type, and duration of the disability and the need of people with this disability for individualized services and supports. Furthermore, every individual who is or was eligible for a diagnosis of mental retardation is eligible for a diagnosis of intellectual disability. In addition, the authors explore why the field is shifting to the term "intellectual disability." Increased understanding is based on a clear distinction among the "construct" used to describe a phenomenon, the "term" used to name the phenomenon, and the "definition" used to precisely explain the term and establish the term's meaning and boundaries. [This article was written with Sharon Borthwick-Duffy, Val Bradley, Wil H. E. Buntinx, David L. Coulter, Ellis (Pat) M. Craig, Sharon C. Gomez, Yves Lachapelle, Alya Reeve, Martha E. Snell, Scott Spreat, Marc J. Tasse, James R. Thompson, Miguel A. Verdugo, Michael L. Wehmeyer, and Mark H. Yeager.]