What nutrition is
An organism needs energy, and it needs materials to build with. The process of obtaining both is nutrition.
Nutrition
The process of obtaining energy and materials in order to maintain life is called nutrition.
What is the energy for?
Life processes such as the growth of the body's cells and the repair of worn-out parts need energy. That energy is obtained through nutrients — that is, through food.
There are two ways of getting food
Organisms fall into two main groups according to how they obtain those nutrients. The next three pages look at both.
Produces its own food. Examples — plants, and most bacteria.
Takes in food produced by other organisms. Examples — all animals, and fungi.
"Nutrition" is not just eating — it is the whole process of obtaining food, digesting it, and getting it into the cell.