Nutrition is the process in which living organism takes in nutrients from the food they eat and these nutrients are needed for energy, maintenance of tissues and regulation of bodily processes. Carbohydrates, fats, proteins, water, vitamins, minerals are some important nutrients required for humans and Nitrogen (N), Phosphorus (P), Potassium (K), Calcium (Ca), Magnesium (Mg), Sulfur (S) are some nutrients required for plants.
Also in other words
Nutrition is the process of nourishing or being nourished, especially the process by which a living organism assimilates food and uses it for growth and for replacement of tissues.