Synopsis, one of:
\frenchspacing \nonfrenchspacing
The first declaration causes LaTeX to treat spacing between sentences in the same way as spacing between words in the middle of a sentence. The second causes spacing between sentences to stretch or shrink more (see \spacefactor); this is the default.
Some typographic traditions, including English, prefer to adjust the space between sentences (or spaces following a question mark, exclamation point, comma, or colon) more than the space between words that are in the middle of a sentence. Declaring \frenchspacing (the command is from plain TeX) switches to the tradition that all spaces are treated equally.
© 2007–2018 Karl Berry
Public Domain Software
http://latexref.xyz/_005cfrenchspacing.html