Importing in Clojure

ns.clj

# As `require.clj` above.
(ns project
  (:require clojure.string
            [clojure.set :as set]))

# As `use.clj` above.
(ns project
  (:use clojure.string
        [clojure.set :only [intersection]]))

# When using `ns`, quoting isn't required.

require.clj

# `require` namespaces imports but namespaced.
(require 'clojure.string ['clojure.set :as 'set])

(def fields
  (set
    (clojure.string/split "Name,Email,Password" #","))) # `split` is namespaced.

(set/intersection #{"Email" "Password" "DOB"} fields) # `intersection` is namespaced to an alias.

use.clj

# `use` imports everything into the current namespace, this could mangle it, for example string, and set both have a `join` function.
(use 'clojure.string '[clojure.set :only [intersection]])

(def fields
  (set
    (split "Name,Email,Password" #","))) # `split` from `clojure.string`.

(intersection #{"Email" "Password" "DOB"} fields) # `intersection` from `clojure.set`.