ns

(ns name clauses...)

Switches to the namespace, creating it, and wires its clauses: :as registers an alias, :refer/:use unqualified names, :import class names for interop, and (:refer-clojure :only ...)/(:refer-clojure :exclude ...) narrow the visible core. There is no :rename. The definitions below the form belong to the namespace. A required namespace other than clojure.string, clojure.set, clojure.java.io (reader only) and clojure.test is a project namespace: one an earlier ns form of the program declared, or one whose file on the source path loads when the clause runs -- once per program, again under :reload (Semantics); a file no root holds is an error.