define

(define variable expression) (define (name formals...) body...) (define (name . rest) body...)

Binds variable to the value of expression; the second and third forms define a procedure, like (define name (lambda formals body...)). At the top level it creates or replaces a global binding, and a user definition of a built-in name such as square wins over the built-in. At the start of a body it is an internal definition, and the internal definitions of a body behave like letrec*. A definition has no value, so the REPL shows nothing. The curried form (define ((f a) b) ...) is not supported.