The Free On-line Dictionary of Computing (30 December 2018):

dot pitch

    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].

   (1995-12-14)