A galaxy having a central bulge surrounded by a flattened disk with no pattern of spiral arms. Lenticular galaxies are intermediate in the Hubble classification system between elliptical and spiral forms and are classified using the designation S0, or SB0 if they have a bar of stars, gas, and dust through the nucleus. Like spiral galaxies, they are disk-shaped with a central bulge, but like elliptical galaxies they contain relatively little gas and dust. Compare elliptical galaxy, irregular galaxy, spiral galaxy. See more at Hubble classification system.