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(texinfo)Command Syntax

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@-Command Syntax
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  The character `@' is used to start special Texinfo commands.  (It has
the same meaning that `\' has in plain TeX.)  Texinfo has four types of
@-command:

1. Non-alphabetic commands.
     These commands consist of an @ followed by a punctuation mark or
     other character that is not part of the alphabet.  Non-alphabetic
     commands are almost always part of the text within a paragraph,
     and never take any argument.  The two characters (@ and the other
     one) are complete in themselves; none is followed by braces.  The
     non-alphabetic commands are: `@.', `@:', `@*', `@SPACE', `@TAB',
     `@NL', `@@', `@{', and `@}'.

2. Alphabetic commands that do not require arguments.
     These commands start with @ followed by a word followed by left-
     and right-hand braces.  These commands insert special symbols in
     the document; they do not require arguments.  For example,
     `@dots{}' => `...', `@equiv{}' => `==', `@TeX{}' => `TeX', and
     `@bullet{}' => `*'.

3. Alphabetic commands that require arguments within braces.
     These commands start with @ followed by a letter or a word,
     followed by an argument within braces.  For example, the command
     `@dfn' indicates the introductory or defining use of a term; it is
     used as follows: `In Texinfo, @@-commands are @dfn{mark-up}
     commands.'

4. Alphabetic commands that occupy an entire line.
     These commands occupy an entire line.  The line starts with @,
     followed by the name of the command (a word); for example,
     `@center' or `@cindex'.  If no argument is needed, the word is
     followed by the end of the line.  If there is an argument, it is
     separated from the command name by a space.  Braces are not used.

  Thus, the alphabetic commands fall into classes that have different
argument syntaxes.  You cannot tell to which class a command belongs by
the appearance of its name, but you can tell by the command's meaning:
if the command stands for a glyph, it is in class 2 and does not
require an argument; if it makes sense to use the command together with
other text as part of a paragraph, the command is in class 3 and must
be followed by an argument in braces; otherwise, it is in class 4 and
uses the rest of the line as its argument.

  The purpose of having a different syntax for commands of classes 3 and
4 is to make Texinfo files easier to read, and also to help the GNU
Emacs paragraph and filling commands work properly.  There is only one
exception to this rule: the command `@refill', which is always used at
the end of a paragraph immediately following the final period or other
punctuation character.  `@refill' takes no argument and does _not_
require braces.  `@refill' never confuses the Emacs paragraph commands
because it cannot appear at the beginning of a line.