An aspect ratio is a mathematical expression for the shape of an image. Standard televisions have an aspect ratio of 1.33:1 (sometimes expressed as 4 x 3), meaning a TV image is one and one-third times as wide as it is high. Most theater screen images are wider than those of television screens, with the two most common theatrical ratios being 1.85:1 and 2.35:1. Other ratios sometimes used are 1.66:1 (standard European format), 1.75:1, 2:1, 2.20:1, 2.55:1 and 2.75:1. Prior to the introduction of widescreen presentations (circa 1953), the theatrical ratio used was 1.33:1, the same as standard TV.