16:9

Widescreen aspect ratio used for film; almost twice as wide as it is high (1.78:1). See also aspect ratio.

16:9 is known as High Definition (HD) and it is the international standard format of HDTV, SD (Standard Definition) TV, and analogue system PALplus.
16:9 ("Sixteen-by-Nine" and "Sixteen-to-Nine") is a widescreen aspect ratio used for films, it has the most common aspect ratio for televisions and computer monitors; almost twice as wide as it is high (1.78:1). See also aspect ratio. It is with a width of 16 units and height of 9. 
16:9 aspect ratio resolutions are 1024×576, 1152×648, 1280×720, 1366×768, 1600×900, 1920×1080, 2560×1440 and 3840×2160.