A feeling of craving something, the term "appetite" is most commonly used in the context of an appetite for food or drink.
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there are a lot of reasons for loss of appetite. 1. indigestion 2. depression 3. anxiety. 4. the look of unappetising food. 5. bowels have not been cleared for quite sometime. 6.mood swings. 7. grief.
physiological hunger.
Do mean hydroxyapatite? Hydroxyapatite is a major component of teeth and bones.