DPI 3 : A unit used to measure the resolution, or sharpness, of a photograph or video image. The unit, an abbreviation for "dots per inch," remains in use even though individual picture elements are now called pixels rather than dots
Russ Rowlett (Director), How Many? A Dictionary of Units of Measurement, Center for Mathematics and Science Education University of North Carolina, USA 2005. http://www.unc.edu/~rowlett/units/dictA.html, (Unit of Meas and Covr Factors - Amer) {608}