Found:

movement

SYNTAX: the process which plays a role in deriving S-structure from D-structure and LF from S-structure by the reordering of constituents. We say that an element at S-structure has been moved if there is a certain relationship between the element and an empty position elsewhere in the structure. EXAMPLE: in the question Who did he see, we interpret who as the direct object of see. This is explained if who is generated in the direct object position at D-structure (to the right of see) and has been moved to the first position in S-structure. This is a case of overt movement because the effect of movement is visible at PF. When movement is involved in the derivation of LF, we speak of hidden or covert movement: the effect is invisible at the level of PF. Thus in a multiple question like Who saw what, the second wh-phrase what is covertly moved to sentence initial position in the derivation of LF (see wh-in-situ).

LIT.	Chomsky, N. (1993) Chomsky, N. (1986b) Chomsky, N. (1973) Chomsky, N. (1965)