The definition of disability under Social Security is different than other programs. Social Security pays only for total disability. No benefits are payable for partial disability or for short-term disability.

"Disability" under Social Security is based on your inability to work. We consider you disabled under Social Security rules if:

You cannot do work that you did before;
We decide that you cannot adjust to other work because of your medical condition(s); and
Your disability has lasted or is expected to last for at least one year or to result in death.
This is a strict definition of disability. Social Security program rules assume that working families have access to other resources to provide support during periods of short-term disabilities, including workers' compensation, insurance, savings and investments.

See http://www.ssa.gov/dibplan/dqualify4.htm for the criteria SS uses to determine disability.

The ADA has a three-part definition of disability that is based on the definition under the Rehabilitation Act and reflects the specific types of discrimination experienced by people with disabilities. Accordingly, it is not the same as the definition of disability under other laws, such as state workers' compensation laws or other federal or state laws, that provide benefits for people with disabilities and disabled veterans.

Under the ADA, an individual with a disability is a person who:

Has a physical or mental impairment that substantially limits one or more major life activities.
Has a record of such an impairment.
Is regarded as having such an impairment.

See http://www.adata.org/about/definition.html#definition