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(elisp)Symbol Type

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Symbol Type
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   A "symbol" in GNU Emacs Lisp is an object with a name.  The symbol
name serves as the printed representation of the symbol.  In ordinary
use, the name is unique--no two symbols have the same name.

   A symbol can serve as a variable, as a function name, or to hold a
property list.  Or it may serve only to be distinct from all other Lisp
objects, so that its presence in a data structure may be recognized
reliably.  In a given context, usually only one of these uses is
intended.  But you can use one symbol in all of these ways,
independently.

   A symbol whose name starts with a colon (`:') is called a "keyword
symbol".  These symbols automatically act as constants, and are
normally used only by comparing an unknown symbol with a few specific
alternatives.

   A symbol name can contain any characters whatever.  Most symbol names
are written with letters, digits, and the punctuation characters
`-+=*/'.  Such names require no special punctuation; the characters of
the name suffice as long as the name does not look like a number.  (If
it does, write a `\' at the beginning of the name to force
interpretation as a symbol.)  The characters `_~!@$%^&:<>{}?' are less
often used but also require no special punctuation.  Any other
characters may be included in a symbol's name by escaping them with a
backslash.  In contrast to its use in strings, however, a backslash in
the name of a symbol simply quotes the single character that follows the
backslash.  For example, in a string, `\t' represents a tab character;
in the name of a symbol, however, `\t' merely quotes the letter `t'.
To have a symbol with a tab character in its name, you must actually
use a tab (preceded with a backslash).  But it's rare to do such a
thing.

     Common Lisp note: In Common Lisp, lower case letters are always
     "folded" to upper case, unless they are explicitly escaped.  In
     Emacs Lisp, upper case and lower case letters are distinct.

   Here are several examples of symbol names.  Note that the `+' in the
fifth example is escaped to prevent it from being read as a number.
This is not necessary in the sixth example because the rest of the name
makes it invalid as a number.

     foo                 ; A symbol named `foo'.
     FOO                 ; A symbol named `FOO', different from `foo'.
     char-to-string      ; A symbol named `char-to-string'.
     1+                  ; A symbol named `1+'
                         ;   (not `+1', which is an integer).
     \+1                 ; A symbol named `+1'
                         ;   (not a very readable name).
     \(*\ 1\ 2\)         ; A symbol named `(* 1 2)' (a worse name).
     +-*/_~!@$%^&=:<>{}  ; A symbol named `+-*/_~!@$%^&=:<>{}'.
                         ;   These characters need not be escaped.

   Normally the Lisp reader interns all symbols (Note: Creating
Symbols).  To prevent interning, you can write `#:' before the name
of the symbol.