catflap.org Online Dictionary Query

  Head Normal Form
       
           (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)