Sub-pixel

A spatial resolution smaller than that of pixels. Although digital images are
composed of pixels it can be very useful to resolve image detail to smaller than pixel
size, i.e., sub-pixel. For example, the data for generating a smooth curve on television
needs to be created to a finer accuracy than the pixel grid itself, otherwise the curve
will look jagged. Again, when tracking an object in a scene or executing a DVE move,
the size and position of the manipulated picture must be calculated, and the picture
resolved, to a far finer accuracy than the pixels, otherwise the move will appear jerky.

See also: Pixel.