@cindex blanks, ignoring leading
@vindex LC_CTYPE
Ignore leading blanks when finding sort keys in each line.
-The @env{LC_CTYPE} locale determines character types.
+By default a blank is a space or a tab, but the @env{LC_CTYPE} locale
+can change this.
@item -d
@itemx --dictionary-order
@vindex LC_CTYPE
Sort in @dfn{phone directory} order: ignore all characters except
letters, digits and blanks when sorting.
-The @env{LC_CTYPE} locale determines character types.
+By default letters and digits are those of @acronym{ASCII} and a blank
+is a space or a tab, but the @env{LC_CTYPE} locale can change this.
@item -f
@itemx --ignore-case
compared in the order @samp{JAN} < @samp{FEB} < @dots{} < @samp{DEC}.
Invalid names compare low to valid names. The @env{LC_TIME} locale
category determines the month spellings.
+By default a blank is a space or a tab, but the @env{LC_CTYPE} locale
+can change this.
@item -n
@itemx --numeric-sort
by a decimal-point character and zero or more digits. A string of
no digits is interpreted as @samp{0}. The @env{LC_NUMERIC}
locale specifies the decimal-point character and thousands separator.
+By default a blank is a space or a tab, but the @env{LC_CTYPE} locale
+can change this.
Numeric sort uses what might be considered an unconventional method to
compare strings representing floating point numbers. Rather than first
Use character @var{separator} as the field separator when finding the
sort keys in each line. By default, fields are separated by the empty
string between a non-blank character and a blank character.
+By default a blank is a space or a tab, but the @env{LC_CTYPE} locale
+can change this.
+
That is, given the input line @w{@samp{ foo bar}}, @command{sort} breaks it
into fields @w{@samp{ foo}} and @w{@samp{ bar}}. The field separator is
not considered to be part of either the field preceding or the field