with the same fan-out and rank 2. Within the LCFRS/MCFG hierarchy, the context-free languages can be characterized by the grammars with fan-out 1; for this fan-out there is no difference between general and well-nested grammars. The TAG-equivalent formalisms can be characterized as well-nested LCFRS/MCFG of fan-out 2. See also Tree-adjoining grammar Linear context-free rewriting system Range concatenation grammar Weir hierarchy Conjunctive grammar References Formal languages