Source : Free On-Line Dictionary of Computing

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)