What is the width of the spaces between the words (by default) that LaTeX uses for text formatting?
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
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:
Put the code above after
The TeXbook explains also the use of
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!