the length of a single line of text. The measure dictates legibility and choice of point size, because the human eye can easily get lost when transitioning from one line to another. This standard depends on space between lines (leading), paragraph justification (raggged right or left justified is more legible, although less traditional) and whether you're printing in American or Euopean standard type faces (in Europe the standard is san-serif, while in America, the more legible serif fonts faces reign). Measure length can kill a book and be more disturbing to a reader than a misspelled word. Author's who also publish can disengage a reader even with the highest quality material by chosing the wrong point size and measure.
Edward C. Patterson