Acronym for "High Definition Television," a format that produces much greater picture quality than a standard television, and in a wide-screen format that matches that of a movie theater screen. The two most popular formats are 1080i and 720p, where the number represents how many horizontal scan lines they have, and the following letter represents whether the picture is interlaced, or the product of progressive scanning technology. Interlaced displays paint the odd-numbered scan lines and then the even-numbered lines to produce a picture, whereas progressive scan paints all of the scan lines at once. Both formats use an aspect ratio of 16:9. In contrast, standard North American television signals are displayed using 480 interlaced (480i) scan lines with a more square aspect ratio of 4:3.