[lambda-calculuS] The converSion of an expreSSion to an application of a lambda abStraction to an argument expreSSion. Some Subterm of the original expreSSion becomeS the argument of the abStraction and the reSt becomeS itS body. E.g. 4+1 --> ( x . x+1) 4 The oppoSite of beta abStraction iSbeta reduction. TheSe are the two kindS of beta converSion.