title: Terminology for methods that mutate or don't mutate state
body: <p>Are there well established terms for referring to methods that do or do not mutate the object state?</p>
  
  <p>For example of a well established term describing a type of function: "<a href="http://www.embeddedrelated.com/showarticle/629.php" rel="nofollow">idempotent</a>".</p>