A petticoat is an article of clothing, a type of undergarment worn under a skirt or a dress. Its precise meaning varies over centuries and between countries. In modern American usage, "petticoat" refers only to a garment hanging from the waist. Petticoats are most often made of cotton, silk, or tulle. They serve three main functions: warmth, creating a fashionable silhouette, and modesty. In historical contexts (16th to mid-19th centuries), petticoat refers to any separate skirt worn with a gown, bedgown, bodice, or jacket. These petticoats were not, strictly speaking, underwear, as they were made to be seen. In both historical and modern contexts, petticoat refers to skirt-like undergarments worn for warmth or to give the skirt or dress the desired attractive shape. Sometimes a petticoat may be called a waist slip or underskirt (UK) or half slip (US), with petticoat restricted to extremely full garments. The term "petticoat" comes from the two words "pety" and "coote," literally meaning "a small coat".