Bottoms are an apparel term used to describe the layers of clothing worn on the bottom half of the body. Bottoms may be in reference to undergarments or outerwear.
About Dresses:
Dresses are a garment for women, which has one piece of material that covers the torso as well as the part of the bottom. The skirt of the dress must come completely around the wearer without any material separating the legs and may be any variety of length.
About Sleeveless:
Sleeveless refers to apparel tops that are characterized by no material covering the arms.
