Wh-in-situ

Definition
Wh-in-situ is a wh-element which has not been moved overtly. In some languages (Japanese for instance), all wh-elements appear in situ; in languages with overt movement of one wh-element (like English), the other wh-elements stay in situ.

Example
what in (i) cannot move because its landing site is taken by who.

(i) I wonder who has bought what?

There is a debate as to what mechanism is responsible for the interpretation of wh-elements in situ. Maybe what in (i) is fronted and adjoined to the embedded clause at LF. This operation is called Wh-raising (in contradistinction to wh-movement, or QR (of non-wh operators)). Another approach is to interpret wh-in-situ without LF-movement, via choice functions. Cases of wh-in-situ are not to be confused with echo-questions like John bought WHAT? : here what's landing site has not been taken by another wh-element.

Links

 * Utrecht Lexicon of Linguistics