A single sac is called a diverticulum. Two or more sacs are called diverticula.
By far, the most common site for diverticula to develop is in the large intestine (colon). Diverticula of the colon occur when the inner layers of the bowel protrude through the outer muscular layers.
Diverticula may also develop in the esophagus (see Esophageal Pouches (Diverticula)) and rarely in the stomach. Meckel diverticulum is a common diverticular disease of the small intestine. It is present at birth in about 2 to 3% of people.
The presence of one or more diverticula in the colon is called diverticulosis. Diverticulosis is a condition that tends to develop during middle age.
If diverticula become inflamed, the condition is called diverticulitis. Diverticulitis can develop with or without infection of a diverticulum.