Most people use anorexia to mean "anorexia nervosa". Technically, though, when the term is used by itself, it simply refers to a reduced desire for food; it doesn't actually imply anything about the causes of that reduction. Anorexia in this sense is a common symptom of several conditions, including gastrointestinal disorders, neurological disorders, and cancer; it's also a side-effect of a wide variety of drugs, some of which are actually designed to produce a decrease in appetite. (I've known a few people who freaked out when they saw "anorexia" listed as a side-effect of a drug--they thought that they were going to end up with low self-esteem, an insatiable desire to exercise, and a distorted body image; in reality, they were going to experience at most a minor reduction in appetite.)