Editing Recursion (section)

==Informal definition==
[[File:Mixing Sourdough starter into the flour.jpg|thumb|[[Sourdough starter]] being stirred into flour to produce sourdough: the recipe calls for some sourdough left over from the last time the same recipe was made.]]

Recursion is the process a procedure goes through when one of the steps of the procedure involves invoking the procedure itself. A procedure that goes through recursion is said to be 'recursive'.<ref>{{Cite web|url=https://www.merriam-webster.com/dictionary/recursive|title=Definition of RECURSIVE|website=www.merriam-webster.com|language=en|access-date=2019-10-24}}</ref>

To understand recursion, one must recognize the distinction between a procedure and the running of a procedure. A procedure is a set of steps based on a set of rules, while the running of a procedure involves actually following the rules and performing the steps.

Recursion is related to, but not the same as, a reference within the specification of a procedure to the execution of some other procedure.

When a procedure is thus defined, this immediately creates the possibility of an endless loop; recursion can only be properly used in a definition if the step in question is skipped in certain cases so that the procedure can complete.

Even if it is properly defined, a recursive procedure is not easy for humans to perform, as it requires distinguishing the new from the old, partially executed invocation of the procedure; this requires some administration as to how far various simultaneous instances of the procedures have progressed. For this reason, recursive definitions are very rare in everyday situations.