Revised(5) Report on the Algorithmic Language Scheme

7.1.6 Programs and definitions

<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>)