Colon

A human colon, and a colon cancer.

In living organisms the colon is the organ in the gastro-intestinal tract that follows directly after the small intestine, and precedes the anus. The colon is sometimes called the "large intestine", even though the small intestine is the longer organ, because it has a larger diameter.

The small intestine is responsible for digestion -- extracting nutrients from the food that passes through it. The large intestines job is to squeeze and otherwise absorb the water from the food residue, before it is excreted, through the anus. When an individual is ill, or the food is toxic, they may excrete food residue that is still wet. This residue is known as diarrhea.