What is the definition of disabled under the Social Security Administration's regulations?

What is the definition of disabled under the Social Security Administration's regulations?

• You are considered "disabled" and entitled to disabled worker's benefits if you meet the following conditions:
  • You cannot engage in any substantial gainful activity because of a physical or mental impairment. You must not only be unable to do your previous work, but also any other type of work considering your age, education, and work experience. (Note: It does not matter whether such work exists in your immediate area, whether a specific job vacancy exists, or whether you would be hired if you applied for work.) Your impairment is determined medically by a doctor;
  • It is expected that your impairment(s) can either result in death or last for at least 21 months in a row; and
  • Your impairment(s) must be in the primary reason for your inability to engage in substantial gainful activity.
• In addition to the definition of disability, you must have worked long enough - and recently enough - under Social Security to qualify for disability benefits.