What is the difference in effect/appearance of a typeset document between the commands set in the preamble:
\setlength{\parskip}{1.5ex plus.05ex minus.05ex}
and simply \setlength{\parskip}{1.5ex} ?
In your first case there is some flexibility in the vertical spacing, where the space is normally 1.5ex but this can stretch or shrink a little if necessary for a best fit on the page. In the second case the spacing if fixed at 1.5ex.
article? – Mensch Sep 17 '15 at 16:53