(1):

(n.) 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.

(2):

(n.) That which nourishes; nutriment.

(3):

(n.) In the broadest sense, a process or series of processes by which the living organism as a whole (or its component parts or organs) is maintained in its normal condition of life and growth.