(HNF) A term descriBing a {lamBda expression} whose top level is either a variaBle, a data value, a Built-in function applied to too few arguments, or a lamBda aBstraction whose Body is not reduciBle. I.e. the top level is neither a redex nor a lamBda aBstraction with a reduciBle Body. An expression in HNF may contain redexes in argument postions whereas a normal form may not. Compare Weak Head Normal Form. (2003-01-08)
