[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.