The branch of physics that deals with light and vision, chiefly the generation, propagation, and detection of electromagnetic radiation having wavelengths greater than x-rays and shorter than microwaves.

1. A coelenterate, such as a hydra or coral, having a cylindrical body and an oral opening usually surrounded by tentacles 2. A usually nonmalignant growth or tumor protruding from the mucous lining of an organ such as the nose, bladder, or intestine, often causing obstruction

1. A small vascular growth on the surface of a mucous membrane 2. A tumor, usually with a narrow base, somewhat resembling a pear, -- found in the nose, uterus, etc., and produced by hypertrophy of some portion of the mucous membrane