The Free On-line Dictionary of Computing (30 December 2018):

alpha conversion

    In lambda-calculus and reduction, the renaming of
   a formal parameter in a lambda abstraction.  This does not
   change the meaning of the abstraction.  For example:

   	\ x . x+1  <-->  \ y . y+1

   If the actual argument to a lambda abstraction contains
   instances of the abstraction's formal parameter then it is
   necessary to rename the parameter before applying the
   abstraction to avoid name capture.

   (1995-05-10)