What is the width of the spaces between the words (by default) that LaTeX uses for text formatting?
2 Answers
The interword space is font dependent, as different fonts require generally different spacing. Moreover it's flexible, to allow justification: it can shrink and stretch.
The values for the default Computer Modern font are
natural width: 3.33 pt
stretch: 1.66pt
shrink: 1.11 pt
The em width in this font is 10pt, so this amounts to saying that the interword space is 1/3 of an em, optimally stretchable up to 1/2 of an em and shrinkable up to 2/9 of an em.
Actually the stretch may go beyond the "optimum", if necessary for justification, but this stretch will contribute to the "badness" computed for the line.
The interword space components for a particular font can be obtained by the following code:
Spacing for the current font:
\the\fontdimen2\font\ plus
\the\fontdimen3\font\ minus
\the\fontdimen4\font
Quad width for the current font: \the\fontdimen6\font
Put the code above after \begin{document}; load in the preamble the necessary packages, for example \usepackage{tgtermes} or similar ones. The code may be also repeated as many times as one wish, inserted in braces and after a font choosing command.
The TeXbook explains also the use of \spaceskip (and \xspaceskip) for changing the interword space from the default established when the font is loaded.
As far as I know, there is no default for that. The width depends by the words that lies in the line and then can be different for every line. This method, together whit hyphenation, allows to TeX to always compose lines correctly!
.but AFAIK also!and?. If you don't want that use\frenchspacing.