let

(let ((var init)...) body...)

Establishes local variable bindings: each init is evaluated (in the surrounding scope, so the bindings are parallel, not sequential) and bound to its var for the duration of body. The body forms are evaluated in order and the value of the last one is returned; with an empty body the result is nil. The bindings are variable bindings only -- per Lisp-2 they do not shadow the function namespace, so a let-bound car does not affect calls to the function car.

If a var names a variable that was proclaimed special (by defvar/defparameter or (declaim (special ...))), that binding is dynamic: it is visible to any function called during body, not just lexically nested code, and is restored when body exits. Ordinary (non-special) names are bound lexically as usual. See also progv for a runtime-computed list of special bindings.