A curtain (sometimes known as a drape, mainly in the United States) is a piece of cloth intended to block or obscure light, or drafts, or water in the case of a shower curtain. A curtain is also the movable screen or drape in a theater that separates the stage from the auditorium or that serves as a backdrop.
Curtains hung over a doorway are known as portières. Curtains are often hung on the inside of a building's windows to block the passage of light, for instance at night to aid sleeping, or to stop light from escaping outside the building (stopping people outside from being able to see inside, often for privacy reasons). In this application, they are also known as "draperies". Curtains come in a variety of shapes, materials, sizes, colors and patterns, and they often have their own sections within department stores, while some shops are completely dedicated to selling curtains.
Curtains vary according to cleanability, ultraviolet light deterioration, oil and dust retention, noise absorption, fire resistance, and life span. Curtains may be moved by hand, with cords, by press-button pads or remote-controlled computers. They are held out of the way of the window by means of curtain tie-backs. Measuring curtain sizes needed for each window varies greatly according to the type of curtain needed, window size, and type and weight of curtain.
Curtains are a form of window treatment, and complete the overall appearance of the house. Window treatment helps control the ambiance and flow of natural light into the room. The effect of drapery or curtains is best seen in daylight, and with proper indoor light positioning, can look attractive even at night.
From evidence found in excavation sites at Olynthus, Pompeii and Herculaneum, portieres appear to have been used as room dividers in classic antiquity. Mosaics from the 2nd to 6th century show curtains suspended from rods spanning arches.