Revised(5) Report on the Algorithmic Language Scheme

5.2 Definitions

Definitions are valid in some, but not all, contexts where expressions are allowed. They are valid only at the top level of a <program> and at the beginning of a <body>.

A definition should have one of the following forms:

(define <variable> <expression>)
(define (<variable> <formals>) <body>) <Formals> should be either a sequence of zero or more variables, or a sequence of one or more variables followed by a space-delimited period and another variable (as in a lambda expression). This form is equivalent to
```
    (define <variable>
      (lambda (<formals>) <body>)).
```
(define (<variable> . <formal>) <body>) <Formal> should be a single variable. This form is equivalent to
```
    (define <variable>
      (lambda <formal> <body>)).
```

Top level definitions
Internal definitions