Dietetics is the science of what people eat and drink, and how that food and drink help or hurt the body. It sits next to nutrition, but it is the practical side: how to plan meals, how to feed someone who is ill, how to use food as part of care. People study dietetics so they can work in hospitals, schools, and clinics. It is a formal, university word. You will see it on a course page far more often than you will hear it at dinner. The ending -ics is the same kind of ending as in mathematics or physics: it names the field. Though actually, everyday English often just says nutrition, even when the course is doing this practical work. Dietetics is not “how to get thin.” Weight can be one small part of it; a baby, a cancer patient, and a footballer all fall inside the same science.