[di-jes-chuh
n, dahy-] 
| 1. | the process in the alimentary canal by which food is broken up physically, as by the action of the teeth, and chemically, as by the action of enzymes, and converted into a substance suitable for absorption and assimilation into the body. |
| 2. | the function or power of digesting food: My digestion is bad. |
| 3. | the act of digesting or the state of being digested. |
The breaking down of food, which is made up of complex organic molecules, into smaller molecules that the body can absorb and use for maintenance and growth.
digestion di·ges·tion (dī-jěs'chən, dĭ-)
n.
The process by which food is converted into substances that can be absorbed and assimilated by the body, especially that accomplished in the alimentary canal by the mechanical and enzymatic breakdown of foods into simpler chemical compounds.