Lenticular galaxies are often considered to be a poorly understood transition state between spiral and elliptical galaxies, which makes its position in the Hubble sequence. The disk have no unique features like spiral arms, which makes them not a spiral galaxies. Its bulge is usually spherical, which makes them not an elliptical galaxies. Lenticular galaxy are divided into subclasses based on their either the amount of dust present or the prominence of a central bar. Galaxies with no central bars are S01, S02 and S03, the numbers indicate the amount of gas absorption in the disk. While the barred galaxies are SB01, SB02 and SB03.