Available since 1.0 (source)
  • (ns name docstring? attr-map? references*)
Sets *ns* to the namespace named by name (unevaluated), creating it
if needed.  references can be zero or more of: (:refer-clojure ...)
(:require ...) (:use ...) (:import ...) (:load ...) (:gen-class)
with the syntax of refer-clojure/require/use/import/load/gen-class
respectively, except the arguments are unevaluated and need not be
quoted. (:gen-class ...), when supplied, defaults to :name
corresponding to the ns name, :main true, :impl-ns same as ns, and
:init-impl-ns true. All options of gen-class are
supported. The :gen-class directive is ignored when not
compiling. If :gen-class is not supplied, when compiled only an
nsname__init.class will be generated. If :refer-clojure is not used, a
default (refer 'clojure.core) is used.  Use of ns is preferred to
individual calls to in-ns/require/use/import:
  (:refer-clojure :exclude [ancestors printf])
  (:require (clojure.contrib sql combinatorics))
  (:use (my.lib this that))
  (:import (java.util Date Timer Random)
           (java.sql Connection Statement)))