The distance between a dot and the closest dot of the same colour (red, green or blue) on a color CRT. Dot pitch is typically from 0.28 to 0.51 mm but large presentation monitors may go up to 1.0 mm. The smaller the dot pitch, the crisper the image, 0.31 or less provides a sharp image, especially when displaying text.
Dot pitch measurements between conventional tubes and Sony's Trinitron tubes are roughly, but not exactly comparable. Sony's CRTs use vertical stripes, not dots, and its measurement is the distance between stripes, not the diagonal distance between dots.
["The Computer Glossary", Alan Freedman].