\frenchspacing & \nonfrenchspacingSynopsis, one of:
\frenchspacing \nonfrenchspacing
The first declaration causes LaTeX to handle spacing between
sentences in the same way as spacing between words in the middle of a
sentence. The second switches back to the default handling in which
spacing between sentences stretches or shrinks more
(see \spacefactor).
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.