There is a difference. Technically the meaning of the word Anorexia is "lack of appetite". However Anorexia Nervosa is not loss of appetite. It entails restricting food with intent. If you lost your appetite and it isn't returning you should see a doctor. Loss of appetite can happen because of many things from stress to Cancer, or medication just to name a few. The weight loss can come with health complications just as in Anorexia Nervosa, you are still at risk of malnutrition if you are not eating sufficiently.

They do refer to loss of appetite as Anorexia, and Anorexia Nervosa when it is an eating disorder. People with Anorexia Nervosa still usually have an appetite to some degree. I see how this can be confusing. I hope that helped a little.