Stack-Sorting Grammar

I propose that, within local domains corresponding to extended projections, typologically possible information-neutral word orders are limited to the stack-sortable (231-avoiding) permutations of a universal head-complement-specifier linear order. This proposal explains and unifies some well-known but previously unrelated word order universals, while successfully generating phenomena that challenge traditional approaches. Applications include Cinque’s revision of Greenberg’s Universal 20, the Final-Over-Final Condition, a modified Head Movement Constraint allowing attested Long Head Movement, English Affix Hopping, Germanic cross-serial subject-verb dependencies, and Icelandic Stylistic Fronting. Extending the system to multiple extended projections requires stack-sorting in cycles, expanding the set of allowed orders.