 The International Classification of Functioning, Disability, and Health (ICF), produced by the World Health Organization, distinguishes between body functions (physiological or psychological, such as vision) and body structures (anatomical parts, such as the eye and related structures).Impairment in bodily structure or function is defined as involving an anomaly, defect, loss or other significant deviation from certain generally accepted population standards, which may fluctuate over time.Activity is defined as the execution of a task or action.