PEL = Pixel = Picture Element. A Pixel can refer to e.g. a RGB tuplet, or a single value. It always indicates just 1 element of the display. The smallest possible displayable element. Half-PEL are used during video processing for extra precision, but for display you can only use integer numbers of pixels. Further subdivisions such as 1/3-pel, quarter-pel, and 1/8-pel are possible depending on the particular video codec algorithm.