In syntax, sluicing is a type of ellipsis that occurs in both direct and indirect interrogative clauses. The ellipsis is introduced by a wh-expression, whereby in most cases, everything except the wh-expression is elided from the clause. Sluicing has been studied in detail in the early 21st century and it is therefore a relatively well-understood type of ellipsis. Sluicing occurs in many languages.
Sluicing is illustrated with the following examples. In each case, an embedded question is understood though only a question word or phrase is pronounced. (The intended interpretations of the question-denoting elliptical clause are given in parentheses; parts of these are anaphoric to the boldface material in the antecedent.)
Sluicing in these examples occurs in indirect questions. It is also frequent in direct questions across speakers, e.g.
The examples of sluicing above have the sluiced material following its antecedent. This material can also precede its antecedent, e.g.
Jason Merchant (2001) states that these and other examples of sluicing can be organized into four categories of sluicing constructions. These types include sluices with adjunct wh-phrases, sluices with overt correlates, sluices with implicit arguments and contrast sluices. The first type refers to when the wh-phrase does not have an elided copy of the antecedent but is an adjunct. The following example from Ali Algryani (2019) shows this:
The second type refers to a correlate in the antecedent clause that is indefinite. This is shown in the above example about someone eating the soup, with ‘someone’ being the indefinite correlate of ‘who’. The third type of sluicing construction refers to when the wh-word is not referring to a term in the antecedent but is referring to an object that corresponds to the preceding verb. The following example from Algryani (2019) shows this:
The final type of sluicing construction occurs when the elided material correspondent contrasts that of what is in the antecedent. The following example from Algryani (2019) shows this:
There are two theoretical approaches that have been proposed for how sluicing occurs in languages. Ross (1969) is the first examination of sluicing; he argued that sluicing involves regular wh-fronting followed by deletion of the sister constituent of the wh-phrase. This analysis has been expanded in greater detail in Merchant (2001), the most comprehensive treatise on sluicing to date. A second kind of analysis is represented by Ginzburg and Sag (2000) and Culicover and Jackendoff (2005), both of which present nonstructural analyses of ellipsis, and do not posit unpronounced elliptical material. Yet another account of sluicing builds on the catena unit; the elided material is a catena.
The movement approach states that sluicing is a product of the syntactic derivation in which an embedded clause is built in the syntax and then the wh-phrase within the embedded clause moves outside of the constituent to the position of SpecCP (specifier to the complementizer phrase). These steps are then followed by the deletion (and therefore non-pronunciation) of the tense phrase node that contains the rest of the clause. Evidence for this approach is seen in the connectivity effects of case marking, binding and preposition stranding as outlined in Merchant (2001).
Interrogative phrases in languages with morphological case-marking show the case appropriate to the understood verb as Ross, (1969) and Merchant, (2001), illustrated here with the German verb "schmeicheln" (to flatter), which governs the dative case on its object.
The sluiced wh-phrase must bear the same case that its counterpart in a non-elided structure would bear Merchant, (2001).
It has been concluded that languages that forbid preposition-stranding in question formation also forbid it in sluicing Merchant (2001), Stjepanovic, (2008), as in the following example from German:
Examples of languages where p-stranding does not occur are Greek, German, and Russian.
Much research has been done to determine if sluicing can allow for preposition-stranding in a non-preposition-stranding language. Stjepanović, (2008) conducted research on whether this is possible in the non-preposition-stranding language, Serbo-Croatian. She concluded that there is not enough evidence to contradict the initial claim made by Ross. However, she did find that a preposition may be lost or removed from a sentence under sluicing in Serbo-Croatian. More research is to be conducted to confirm the official cause of this preposition-loss.
An example of the preposition-loss shown by Stjepanović, (2008) is displayed below.
Merchant (2003) demonstrates that binding supports the movement approach using the following sentence:
In order for the second “his work” to refer to “every linguist” in the above example, it must be c-commanded by its antecedent within its local domain. Here, “his work” could not be coreferential with the subject: “every linguist” at the beginning of the sentence because it is outside of its local domain. This provides evidence that “his work” originally started off in the elided constituent where it could be c-commanded and in the local domain of that “every linguist” before it moved out of the clause.
There are also several theoretical approaches to sluicing that do not involve the movement of the wh-phrase out of the embedded clause. These approaches include PF deletion and LF copying. PF deletion as proposed in Lasnik (2007) states that the TP within the embedded clause is null and has syntactic structure within it that is elided following a wh-movement operation. The other approach, LF copying, is a process proposed by Lobeck (1995) in which the original structure of a sluicing phrase is one in which the wh-word originates in the SpecCP position of the embedded clause and a null phrase marker (marked e) occupies the position of the tense phrase of the embedded clause. This is the extent of the syntactic derivation. After this structure is derived, it is sent off for semantic interpretation, to logical form, in which the implied material in the tense phrase is then present for our full understanding of the sentence. The evidence for this approach is that it is able to account for islands in sluicing as is discussed below.
Sluicing allows a sentence that contains an island to retain its meaning and remain grammatical. As mentioned by Abels, (2018), there is an ongoing debate on whether this can happen in all situations or if it is island dependent.
The first example is ungrammatical because the island prevents us from moving anything out of the subject constituent (shown in square brackets). The second example is saved through sluicing as the island is sluiced and the meaning can be inferred from the context of the sentence, therefore maintaining the meaning and remaining grammatical.
In some languages, sluicing can leave behind more than one wh-phrase (multiple remnant sluicing):
Sentences like these are considered acceptable in languages like German, Japanese, Chinese, Turkish, Russian, and others, although in English, their acceptability seems marginal (but see Bolinger 1978, Merchant 2001, and Richards 2010 for examples). Lasnik 2014 discusses the fact that the wh-phrase remnants in multiple sluicing must be clausemates:
Only the catena-based approach handles multiple sluicing without further elaboration. The structural movement analysis must rely on some other type of movement to evacuate the noninitial wh-phrase from the ellipsis site; proposals for this additional movement include extraposition or shifting and need to be able to account for islands in sluicing. The nonstructural analysis must add phrase-structure rules to allow an interrogative clause to consist of multiple wh-phrases and be able to account for connectivity effects. The catena-based approach, however, does not account for the locality facts; since catenae can span multiple clauses, the fact that multiply-sluiced wh-phrases must be clausemates is a mystery.
Sluicing has also been analyzed in Omani Arabi as is shown in Algryani (2019). All four of the above stated sluicing constructions outlined by Merchant (2001) are accounted for in Omani Arabic.
Algryani (2019) displays the different constructions in the following examples:
Sluices with Adjunct Wh-Phrases
Sluices with Overt Correlates
Sluices with Implicit Arguments
The following example from Merchant, (2003) displays sluicing in Danish:
The following example from Abels, (2018) displays sluicing in German:
The following example from Merchant (2003) displays sluicing in Japanese:
The following example from Kim & Sells (2013) displays sluicing in Korean: