‘When I use a word, it means just what I choose it to mean’. So it is with rehabilitation, except that several definitions and explanations have been proposed. Although the similarities between the definitions are considerable and far eclipse any differences, the perceived diversity of view has contributed to confusion over the purpose and process of rehabilitation. Is it ‘elderly care’? Is it ‘therapy’? Is it ‘post-acute’ care? The apparent ambiguity and the intangible qualities of rehabilitation contrast with the concrete ‘ologies’ of contemporary organ-based medicine and contribute to its vulnerability in our modern general hospitals. Pressures caused by rising emergency admissions and cost-driven bed closures have necessitated steadily reducing lengths of stay and rehabilitation, as a less visible component of care, has tended to be squeezed out. Paradoxically, the consequences of the ‘sicker and quicker’ discharge approach, with fresh burdens placed on community health and social services, have drawn attention to rehabilitation as a missing ingredient. We have now entered a phase of rediscovering at a strategic policy level the rehabilitation needs of older people but redefined in new terminology as ‘recuperation’ or ‘recovery’ This article will describe the core concepts of rehabilitation for older people and set the scene for forthcoming articles addressing specific rehabilitation topics.