Pied-piping
In linguistics, pied-piping is a phenomenon of syntax whereby a given focused expression brings along an encompassing phrase with it when it is moved.
The term was introduced by John Robert Ross in 1967. It references the legend of the Pied Piper of Hamelin, where a piper lures rats and children away from their town. In syntactic pied-piping, a focused expression (such as an interrogative word) pulls its host phrase with it when it moves to its new position in the sentence. Metaphorically, the focused expression is the piper, and the host phrase is the material being pied-piped.
Pied-piping is an aspect of syntactic discontinuities and has to do with constituents that can or cannot be discontinuous. Pied-piping is most visible in cases of wh-fronting of information questions and relative clauses, but it is not limited to wh-fronting. It can also occur with almost any type of discontinuity, including extraposition, scrambling, and topicalization. Most, if not all, languages that allow discontinuities employ pied-piping to some extent. However, there are significant differences across languages in this area, with some languages using pied-piping much more than others.