Shorthand term for picture element, or the smallest point or dot on a computer monitor. Any computer display is divided into rows and columns of tiny dots, which are individual points at which the scanning electron beam has hit the phosphor-coated screen. The pixel is the smallest indivisible point of display on a monitor. The dot pitch is the measure of the diameter of an individual pixel; a monitor with a dot pitch of .28, for example, is composed of pixels .28 millimeter in diameter. The number of pixels per inch or lines of pixels per inch is a measure of screen resolution. It is commonly expressed as the horizontal and vertical dimensions of the pixel array; for example, a monitor described as 640 x 480 possesses 640 pixels across by 480 pixels down. The greater the number of pixels per inch, the better the resolution. The measure of the number of bits used to describe a pixel is known as color depth. (See Color Depth.) A pixel is also known as a pel, which is also short for picture element.
The term pixel is also used to refer to the smallest point that a scanner can detect, or is synonymous with the sampling rate of the scanner. A scanner that takes 500 samples per inch (or, in other words, 500 discrete points of imaging each inch) can be said to have a resolution of 500 pixels per inch (also known as dots per inch. The resolution at which a scanner will capture an image can be varied.
The term pixel is also used to refer to the individual printer spots that make up an image produced on a laser printer or imagesetter or other digital output device. These pixels are more commonly down as "dots" or, more correctly, "spots."