Frailty is a common clinical syndrome in older adults associated with increased risk of poor health outcomes, including falls, disability, hospitalization, and mortality. It is characterized by a mutually exacerbating cycle of negative energy balance, sarcopenia, and diminished strength. Fried and colleagues proposed a clinical phenotype of frailty with five criteria: low grip strength, low energy, slowed waking speed, low physical activity, and unintentional weight loss. A pre-frail stage, where one or two criteria are present, identifies individuals at high risk of progressing to frailty. Alternative definitions include the frailty index (FI), which counts accumulated deficits over time, but Fried's phenotype is more widely used due to its clinical relevance and theoretical framework. The natural history of frailty involves a progressive decline in multiple physiological systems, with weakness often being the first manifestation. Frailty transitions between states (non-frail, pre-frail, frail) are common, with a higher prevalence in older adults and women. Frailty is not an irreversible process but can be mitigated through early intervention. Behavioral precursors, such as reduced life-space mobility, are linked to frailty development. Frailty is a medical syndrome characterized by co-occurring signs and symptoms, supported by epidemiological data showing its prevalence in older populations. Frailty is associated with increased mortality and adverse health outcomes, and its identification is crucial for targeted interventions. While the exact mechanisms of frailty are still under investigation, research highlights the importance of early detection and prevention strategies. The debate over operational definitions of frailty and its relationship with aging, disability, and chronic diseases underscores the need for further research to better understand and quantify frailty's underlying mechanisms. Despite ongoing discussions, the severe impact of frailty on older adults and society is widely recognized, emphasizing the importance of developing effective interventions to prevent or alleviate its effects.Frailty is a common clinical syndrome in older adults associated with increased risk of poor health outcomes, including falls, disability, hospitalization, and mortality. It is characterized by a mutually exacerbating cycle of negative energy balance, sarcopenia, and diminished strength. Fried and colleagues proposed a clinical phenotype of frailty with five criteria: low grip strength, low energy, slowed waking speed, low physical activity, and unintentional weight loss. A pre-frail stage, where one or two criteria are present, identifies individuals at high risk of progressing to frailty. Alternative definitions include the frailty index (FI), which counts accumulated deficits over time, but Fried's phenotype is more widely used due to its clinical relevance and theoretical framework. The natural history of frailty involves a progressive decline in multiple physiological systems, with weakness often being the first manifestation. Frailty transitions between states (non-frail, pre-frail, frail) are common, with a higher prevalence in older adults and women. Frailty is not an irreversible process but can be mitigated through early intervention. Behavioral precursors, such as reduced life-space mobility, are linked to frailty development. Frailty is a medical syndrome characterized by co-occurring signs and symptoms, supported by epidemiological data showing its prevalence in older populations. Frailty is associated with increased mortality and adverse health outcomes, and its identification is crucial for targeted interventions. While the exact mechanisms of frailty are still under investigation, research highlights the importance of early detection and prevention strategies. The debate over operational definitions of frailty and its relationship with aging, disability, and chronic diseases underscores the need for further research to better understand and quantify frailty's underlying mechanisms. Despite ongoing discussions, the severe impact of frailty on older adults and society is widely recognized, emphasizing the importance of developing effective interventions to prevent or alleviate its effects.