query: What is 4k?
passage: 4K resolution
4K resolution, also called 4K, refers to a horizontal display resolution of approximately 4,000 pixels.[1] Digital television and digital cinematography commonly use several different 4K resolutions. In television and consumer media, 3840×2160 (4K UHD) is the dominant 4K standard, whereas the movie projection industry uses 4096×2160 (DCI 4K).
passage: Ultra-high-definition television
On October 18, 2012, the Consumer Electronics Association (CEA) announced that it had been unanimously agreed on by a vote of the CEA's Board of Industry Leaders that the term "Ultra High-Definition", or "Ultra HD", would be used for displays that have a resolution of at least 8 megapixels with a vertical resolution of at least 2,160 pixels and a horizontal resolution of at least 3,840 pixels. The Ultra HD label also requires the display to have an aspect ratio of 16:9 or wider and to have at least one digital input that can carry and present a native video signal of 3840x2160 without having to rely on a video scaler. Sony announced they would market their 4K products as "4K Ultra High-Definition (4K UHD)".