Gamut. If you don’t have a background on the technical side of television this may be a new term for you. Think colorimetry.
We don’t have a full palette of red, green, and blue to mix when we create a color image. Gamut is the quality related to how much of the full color space we can truthfully represent without artifacts or distortion. The new 4K technology lets us carve out a bigger chunk of the color space.
For me the attractive feature in the 4K capable hardware is the enhanced dynamic range provided by the new sensors. This article from Dave Kendricksen, found at nofilmschool.com, would have us believe that the end of interlacing and an expanding gamut are the key features to be had in the new technology.