Disability is inability to do what one is capable of,by own definition though. Disability is an impairment that may be cognitive, developmental, intellectual, mental, physical, sensory.
When is one said to have disabilities?
It has different contextual meaning 
So what are the contextual meanings you alluded?
view as needing to be fixed (the medical model). It may refer to limitations imposed on people by the constraints of an ableist society (the social model). Or the term may serve to refer to the identity of disabled people. Physiological functional capacity (PFC) is a related term that describes an individual's performance level. It gauges one's ability to perform the physical tasks of daily life and the ease with which these tasks are performed. PFC declines with advancing age to result in frailty, cognitive disorders
Disability
According to many definitions, a disability is an impairment that may be cognitive, developmental, intellectual, mental, physical, sensory, or some combination of these. Other definitions describe disability as the societal disadvantage arising from such impairments. Disability substantially affects a person's life activities and may be present from birth or occur during a person's lifetime.
Disability is a contested concept, with different meanings in different communities. It may be used to refer to physical or mental attributes that some institutions, particularly medicine,