Intestinal is the describing word for the intestine: the long tube in your body that food moves through after it leaves the stomach. Doctors put it in front of other words: intestinal pain, an intestinal infection, intestinal bacteria. It is a medical, slightly formal word; at the dinner table people just say stomach, tummy, or guts, even when they mean this tube. Though actually, “stomach” in everyday talk is often loose — a lot of what people call a stomach ache is happening further along, in the intestine. There is a small intestine and a large intestine, and intestinal can point to either, or to the whole path.