Polypus, or polyp (plural: polypi), is a general name applied to tumours which are attached by a stalk to the surface from which they spring. The term refers only to the shape of the growth and has nothing to do with its structure or nature. Most polypi are harmless, although malignant polypi are also found. The usual structure of a polypus is that of a fine fibrous core covered with epithelium resembling that of the surrounding surface. The sites in which polypi are most usually found are the interior of the nose, the outer meatus of the ear, and the interior of the womb, bladder, or bowels.
A polyp typically originates from a mucous membrane and is attached to it via a stalk or pedicle. Polyps can be located in various areas of the body, including the nasal passages, urinary bladder, stomach, large intestine, or uterus.