beta reduction

from The Free On-line Dictionary of Computing (8 July 2008)

beta reduction

   [{lambda-calculus}] The {application} of a {lambda
   abstraction} to an argument expression.  A copy of the body of
   the lambda abstraction is made and occurrences of the {bound
   variable} being replaced by the argument.  E.g.

   	(\ x . x+1) 4  -->  4+1

   Beta reduction is the only kind of {reduction} in the {pure
   lambda-calculus}.  The opposite of beta reduction is {beta
   abstraction}.  These are the two kinds of {beta conversion}.

   See also {name capture}.