Abstract The term “frailty” is used loosely to describe a range of conditions in older people, including general debility and cognitive impairment. There is no clear consensus on the definition of frailty; however, it is proposed that frailty comprises a collection of biomedical factors which influences an individual's physiological state in a way that reduces his or her capacity to withstand environmental stresses. Only a subset of older people are at risk of becoming frail; these are vulnerable, prone to dependency and have reduced life expectancy. These health outcomes contribute to an increased demand for medical and social care, and are associated with increased economic costs. As demographic trends indicate a rise in the older population, this healthcare burden will increase. This review aims to encapsulate the current debate surrounding the concept of frailty, with emphasis on proposed definitions of frailty which may be relevant to its identification in the clinical setting.