[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.