Frozen Structure Constraint
Frozen Structure Constraint is a constraint formulated in Ross (1967) which says that if a clause has been extraposed from a NP whose head noun is lexical, this NP may not be moved, nor may any element of the clause be moved out of that clause. The first part is illustrated in (i), the second part in (ii).
(i) * [NP Which packages ti ]j didn't Sam pick up tj until it had stopped raining [which are to be mailed tomorrow]i (ii) * The coat [whichi a girl tj came in [Sj who had worn ti]] was torn
- Ross, J.R. 1967. Constraints on variables in syntax, doctoral dissertation, MIT (published as 'Infinite syntax!' Ablex, Norwood (1986)).