Disability is defined differently by different social groups. For medical and benefit purposes, disability is typically seen an impairment that may be cognitive, developmental, intellectual, mental, physical, sensory, or some combination of these. It substantially affects a person's life activities and may be present from birth or occur during a person's lifetime. There are different definitions of disability that can serve different purposes. For example, in the USA, Social Security Administration defines it as a person who cannot work as before; the administration decides that the disabled person cannot adjust to the work because of medical conditions; and/or that the disability has lasted or is expected to last for at least one year or to result in death. The UN Convention offers an important view that persons with disability have human rights. Specifically, "The Convention is intended as a human rights instrument with an explicit, social development dimension. It adopts a broad categorization of persons with disabilities and reaffirms that all persons with all types of disabilities must enjoy all human rights and fundamental freedoms. It clarifies and qualifies how all categories of rights apply to persons with disabilities and identifies areas where adaptations have to be made for persons with disabilities to effectively exercise their rights and areas where their rights have been violated, and where protection of rights must be reinforced."