. Lexical Elements of LISP
Most LISP's use a subset of ASCII:
.See http://www/dick/samples/comp.text.ASCII.html
space::=" "| CR | LF | HT |... .  
white_space::= space #space.  One or more space characters.
char::=`any ASCII character`.
digit::= "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9" | "0".
letter::= "A".."Z" | "a".."z",
sign::= "+" | "-".
quote::="\"",  
comma::=",",
period::=".", 
parenthesis::="(" | ")",
back_quote::="`", 
at_sign::="@", ,
semicolon::=";"
hash_sign::="#",...

. Lexical Analysis
The LISP interpreter first does a lexical analysis of all input and splits up
the input into delimiters and atoms, while discarding whitespace:
lexical_input::=  #( $atom | $delimiter | $dot | $whitespace | $comment),
lexical_output::= #( $atom | $delimiter | $dot ).

In many LISPs atoms that are not strings or numbers are converted
to upper case.  In other LISPs the same atoms are converted to
lower case.

The $dot (a $period) separated from an $atom or $number is use to idicate
the fundamental data structure in LISP of the dotted pair: "( FIRST . SECOND)".

. Lexemes
comment::= $semicolon #$char $end_of_line.

delimiter::= $comma | $parenthesis | $brackets | ...,

For x, non(x)::= $char~(x). 
	O::=$optional,
	optional(x)::= (x|).

string::= $quote #$non($quote) $quote,
.As_is 		"string"
 Strings are atoms that can include spaces and
where the case of the letters is significant.

number::= $fixed_point_number |$floating_point_number,

fixed_point_number::= $optional($sign) $digit #$digit,

floating_point_number::= $optional($sign) $digit #$digit $period $digit #$digit,
	-- floating point is not available in every LISP.

atom::= $string | $number | $word, -- an atom is the fundamental unit of data in LISP.

word::=$non_numeric_lexeme~$dot, A word can not be a sigle $dot or a $number but it can be any string of non-space and non-delimeter characters.

non_numeric_lexeme::=#$non($space|$delimiter) $non($digit) #$non($space|$delimiter). -- one or more characters with at least one non-digit.
Notice that a word that has no letter is treated as a number.  Things
like '*2'  and '2a' are valid words!

dot::=$period.

. Special Atoms
	nil::="NIL"|"nil", -- indicates an empty list.
	false::=$nil,
	true::= "T" | "t",
	true::$scheme= "#t",
	false::=$scheme= "#f",
	lambda::="LAMBDA" | "lambda", -- operator indicating a function
	cond::="COND" | "cond", -- operator for conditional expressions.
	define::$scheme="DEFINE" | "define", -- operator that defines a function.
	defun::="DEFUN" | "defun", -- operator that defines a function.
	car::="CAR" | "car", -- function return the front of a list
	cdr::="CDR" | "cdr", -- function returning the rest of a list.
	cons::="CONS"|"cons",-- a function that constructs a CAR/CDR pair.
	progn::="PROGN" | "progn", -- an operator for constructing blocks and compound statements.
	let::="LET" | "LET", -- an operator for constructing blocks with local variables.
	... .
There are a great many other ready made functions in most LISPs, for example
in the XLISP implemented at CSUSB:
.See http://www/dick/samples/lisp.functions.html
. Glossary
scheme::=a modern simplified and statically scoped LISP.