13.  Spaces, Again

      The only way EQN can deduce that some sequence of letters might be special is if that sequence is separated from the letters on either side of it. This can be done by surrounding a special word by ordinary spaces (or tabs or newlines), as we did in the previous section.

      You can also make special words stand out by surrounding them with tildes or circumflexes: x~=~2~pi~int~sin~(~omega~t~)~dt
is much the same as the last example, except that the tildes not only separate the magic words like sin, omega, and so on, but also add extra spaces, one space per tilde:

      Special words can also be separated by braces { } and double quotes "...", which have special meanings that we will see soon.