Anorexia nervosa, often referred to simply as anorexia, is an eating disorder characterized by low weight, food restriction, body image disturbance, fear of gaining weight, and an overpowering desire to be thin. Anorexia is a term of Greek origin: an- (ἀν-, prefix denoting negation) and orexis (ὄρεξις, "appetite"), translating literally to "a loss of appetite"; the adjective nervosa indicating the functional and non-organic nature of the disorder. Anorexia nervosa was coined by Gull in 1873 but, despite literal translation, the feeling of hunger is frequently present and the pathological control of this instinct is a source of satisfaction for the patients.