\frenchspacing & \nonfrenchspacing ¶Synopsis, one of:
\frenchspacing \nonfrenchspacing
\frenchspacing causes LaTeX to make spacing after all
punctuation, including periods, be the same as the space between words
in the middle of a sentence. \nonfrenchspacing switches back
to the default handling in which spacing after most punctuation stretches
or shrinks differently than a word space (see \spacefactor).
In American English, the typesetting tradition is to adjust, typically
increasing, the space after punctuation more than the space between
words that are in the middle of a sentence. Declaring
\frenchspacing (the command is inherited from plain TeX)
switches to the tradition that all spaces are treated equally.
If your LaTeX document specifies the language being used, for
example with the babel package, the necessary settings
should be taken care of for you.