@kindex SPC @r{(Incremental search)}
@findex isearch-toggle-lax-whitespace
@vindex search-whitespace-regexp
- By default, search commands perform @dfn{lax space matching}:
-each space, or sequence of spaces, matches any sequence of one or more
-whitespace characters in the text. (Incremental regexp search has a
-separate default; see @ref{Regexp Search}.) Hence, @w{@samp{foo bar}}
-matches @w{@samp{foo bar}}, @w{@samp{foo@ @ bar}},
-@w{@samp{foo@ @ @ bar}}, and so on (but not @samp{foobar}). More
-precisely, Emacs matches each sequence of space characters in the
-search string to a regular expression specified by the variable
-@code{search-whitespace-regexp}. For example, to make spaces match
-sequences of newlines as well as spaces, set it to the regular expression
-@samp{[[:space:]\n]+}. The default value of this variable considers
-any sequence of spaces and tab characters as whitespace.
+ By default, search commands perform @dfn{lax space matching}: each
+space, or sequence of spaces, matches any sequence of one or more
+whitespace characters in the text. More precisely, Emacs matches each
+sequence of space characters in the search string to a regular
+expression specified by the user option
+@code{search-whitespace-regexp}. The default value of this option
+considers any sequence of spaces and tab characters as whitespace.
+Hence, @w{@samp{foo bar}} matches @w{@samp{foo bar}}, @w{@samp{foo@ @
+bar}}, @w{@samp{foo@ @ @ bar}}, and so on (but not @samp{foobar}). If
+you want to make spaces match sequences of newlines as well as spaces
+and tabs, customize the option to make its value be the regular
+expression @samp{[[:space:]\n]+}. (The default behavior of the
+incremental regexp search is different; see @ref{Regexp Search}.)
If you want whitespace characters to match exactly, you can turn lax
space matching off by typing @kbd{M-s @key{SPC}}