nutrition

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun 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.
• noun The science or study that deals with food and nourishment, especially in humans.
• noun A source of nourishment; food.

from The Century Dictionary.

• noun The act or process by which organisms, whether vegetable or animal, absorb into their system their proper food and build it into their living tissues.
• noun That which nourishes; nutriment.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Physiol.) In the broadest sense, a process or series of processes by which a living organism as a whole (or its component parts or organs) is maintained in its normal condition of life and growth.
• noun (Physiol.) In a more limited sense, the process by which the living tissues take up, from the blood, matters necessary either for their repair or for the performance of their healthy functions.
• noun That which nourishes; nutriment.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun The organic process by which an organism assimilates food and uses it for growth and maintenance.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a source of materials to nourish the body
• noun the scientific study of food and drink (especially in humans)
• noun (physiology) the organic process of nourishing or being nourished; the processes by which an organism assimilates food and uses it for growth and maintenance