About 15% of the world's population lives with some form of disability, or whom 2-4% experience significant difficulties in functioning (WHO, 2011). For the U.S. Federal Government, with respect to an individual, the term "disability" means:
(A) a physical or mental impairment that substantially limits one or more of the major life activities of such individual;
(B) a record of such an impairment; or
C) being regarded as having such an impairment.
In addition, others expand such definition to explain that a disability is a condition or function judged to be significantly impaired relative to the usual standard of an individual or group. The term is used to refer to individual functioning, including physical impairment, sensory impairment, cognitive impairment, intellectual impairment mental illness, and various types of chronic disease (Disabled-World, 2011).