TeX "glue" (stretch and shrink)

[Gordon Haverland]

On Thu, 3 Oct 2019 07:53:40 -0600 (MDT)
Doug McKenna <doug at mathemaesthetics.com> wrote:

> The first thought that came to mind trying to understand the question
> was maybe the typographic concept of "rivers" and how to avoid them
> was applicable.  A river on a typographic page is an unplanned-for,
> mostly vertical alignment of spaces that becomes visually prominent
> and undesired.

I know of widows and orphans, I had never heard of rivers.  Is "rivers"
the best term to search for on this?

Gord