A program transfORmation to remove free variables. An expression containing a free variable is replaced by a function applied to that variable. E.g. f x = g 3 where g y = y + x x is a free variable of g so it is added as an extra argument: f x = g 3 x where g y x = y + x Functions like this with no free variables are known as supercombinatORs and are traditionally given upper-case names beginning with "$". This transfORmation tends to produce many supercombinatORs of the fORm f x = g x which can be eliminated by eta reduction and substitution. Changing the ORder of the parameters may also allow mORe optimisations. References to global (top-level) constants and functions are not transfORmed to function parameters though they are technically free variables. A closely related technique is closure conversion. See also Full laziness.