Overview
The National Cancer Institute defines “disorder” thusly:
“In medicine, an abnormal condition that affects the body’s function but may or may not have specific signs and symptoms. A disorder may indicate that a specific disease is present, but there is usually not enough evidence to make a diagnosis. There are many different types of disorders, including physical, mental, emotional, behavioral, genetic, and functional disorders.”
If you read the entry on disease, the two definitions sound essentially synonymous. Diseases, disorders, and disabilities all have overlaps and technical meanings with fuzzy boundaries in their scope. Generally though, diseases involves an observable physiological or psychological source of abnormality like cell damage from bodily trauma or some kind of pathogen like bacteria or a virus. Disorders refer to collections of symptoms that are abnormal, which may or may not be caused by a disease. Disabilities involve some incongruence between one’s body and one’s environment such that the body is not able to function as other bodies do, and they may be caused by a disease or determined by a disorder.