Sluicing

"Sluicing also means extracting metals or gems in placer mining operations using a sluice box".

In syntax, sluicing designates a grammatical structure in which a clause is represented only by a wh- phrase. Examples of sluicing in English include:

(1) :Phoebe wants to eat something, but she doesn't know what "e".
(2) :Jon doesn't like the lentils, but he doesn't know why "e".

The e marks where ellipsis happened.

Although sluicing is most commonly found embedded under predicates such as know or remember, main clause sluicing is also possible, as a reply to an independent utterance, e.g.,

(3) - Somebody is coming for dinner tonight.
- Who e?

In some languages, it's possible to sluice more than once, according to [http://home.uchicago.edu/~merchant/ Jason Merchant] . Constructions like
(4) :*Someone wants to eat something, but I don't know who "e" what.
are considered grammatical in languages like Japanese, Turkish, and Russian.

Sluicing was analyzed and so named by John Robert Ross in his 1969 CLS paper "Guess who?". Sluicing raises a potential problem for syntax, as the elided content seems to form a non-constituent. Ross's solution was to analyse sluicing as involving regular wh- fronting followed by ellipsis of the sister constituent of the wh- phrase. This analysis has been expanded in greater detail in "The syntax of silence: Sluicing, islands, and the theory of ellipsis" (Merchant, 2001 Oxford), which is the most comprehensive treatise on sluicing and ellipsis. However, as with most work on ellipsis, reading Ross's work is a good place to start understanding it.