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?
refer to limitations imposed on people by the constraints of an ableist society
Are there laws that protects people with disabilities?
or physical disorders, all of which may lead to labeling individuals as disabled.
The discussion over disability's definition arose out of disability activism in the United States and the United Kingdom in the 1970s, which challenged how the medical concept of disability dominated perception and discourse about disabilities. Debates about proper terminology and their implied politics continue in disability communities and the academic field of disability studies. In some countries, the law requires that disabilities are documented by a healthcare provider in order to assess qualifications for disability benefits.
Types
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,