This document defines nutrition and dietetics, describing how foods are classified by origin, chemical composition, and nutritive value. It explains that dietetics involves planning meals for the well and sick based on nutritional needs, food habits, and disease factors. Diets are modified as liquid, full fluid, soft, or light depending on a patient's condition, with liquid diets used short-term for pre/post-op stages and full fluids for those unable to chew/swallow solid food. Dietetics helps treat deficiency diseases, gastrointestinal issues, kidney/heart/liver problems, and more.