Which combining form refers to a sac or pouch in the walls of a canal or organ?

• A. Arc/o
• B. Xer/o
• C. Diverticul/o
• D. Tympan/o

Answer: (C)

A diverticulum is a sac or pouch that forms in the wall of a hollow organ. The combining form diverticul/o denotes this structure, so terms built with it describe a pouch within the organ wall—such as diverticulosis or diverticulitis in the colon. The other forms point to different ideas: arc/o relates to a bend or arc, xer/o means dry, and tympan/o refers to the eardrum. Thus, diverticul/o is the one that specifically means a sac or pouch in the walls of a canal or organ.