<program> –> <command or definition>*
<command or definition> –> <command>
| <definition>
| <syntax definition>
| (begin <command or definition>+)
<definition> –> (define <variable> <expression>)
| (define (<variable> <def formals>) <body>)
| (begin <definition>*)
<def formals> –> <variable>*
| <variable>* . <variable>
<syntax definition> –>
(define-syntax <keyword> <transformer spec>)