Functional status is an individual's ability to perform normal daily activities required to meet basic needs, fulfill usual roles, and maintain health and well-being. Functional status subsumes(包括) related concepts of interest: functional capacity and functional performance. While functional capacity represents an individual's maximum capacity to perform daily activities in the physical, psychological, social, and spiritual domains of life, functional performance refers to the activities people actually do during the course of their daily lives. A maximal exercise test measures physical functional capacity, while a self-report of activities of daily living measures functional performance.

Functional status can be influenced by biological or physiological impairment, symptoms, mood, and other factors. It is also likely to be influenced by health perceptions. For example, a person whom most would judge to be well but who views himself as ill may have a low level of functional performance in relation to his capacity.