A cluster of symptoms,including falls,disability,cognitive impairment,decreased autonomic activity,unintentional weight loss and fatigue,are common in older people.This “core symptom complex” defines frailty.Frailty is often related to malnutrition,but is distinguished with the presence of sarcopenia.Frailty embodies a decline in a patient\'s overall function,which is not entirely explained by a loss of skeletal muscle mass or decreases in muscle function.Frailty occurs when the individual\'s physiological reserve decreases in conjunction with internal dynamic balance disorders and physiological debility.Frailty is associated with adverse clinical outcomes including an increased risk of complications of other conditions and surgery,unintentional injury (falls and fractures),disability,a poor quality of life,and even death.Frailty is common not only in the elderly,but also in patients with cancer,cardiovascular diseases,respiratory diseases,and malnutrition.The prevalence of frailty has been reported to be between 4.0％-59.1％in different reports,and increases with age.Frailty can be diagnosed by the presence of the core symptom complex (frailty phenotype) or based on the frailty index.Early assessment and treatment can significantly improve the health prognosis of patients.Treatments aimed at maintaining an individual\'s homeostasis can be more beneficial for preventing or resolving frailty than specifically treating any underlying disease(s).Improving the patient\'s nutritional status,implementing physical exercise,and developing individualized multidisciplinary interventions may be the best ways to prevent adverse clinical outcomes in patients with frailty.This article reviews the definitions,diagnosis,epidemiology,etiology and pathogenesis of frailty,as well as the interventions that can be used to combat frailty.