Wh-movement (or wh-fronting or wh-extraction or A'-movement) is a syntactic phenomenon found in many languages around the world, in which interrogative words (sometimes called wh-words) or phrases show a special word order. Unlike ordinary phrases, such wh-words appear at the beginning of an interrogative clause. The term wh-movement is used because most English interrogative words start with wh-, for example, who(m), whose, what, which, when, where, why, etc. (though how is an exception). The term wh-movement tends to be applied to similar word order permutations in languages other than English as well,[1] even when the interrogative words of a given language do not start with wh- (though some authors use the term A'-movement to avoid confusion).
Because of variation in analyses and terminology, wh-movement constructions are sometimes referred to as long-distance dependencies or unbounded dependencies. These names are most commonly used by linguists who work with non-transformational approaches like lexical functional grammar and head-driven phrase structure grammar.
According to Joseph Greenberg's linguistic universal No.12, "If a language has dominant order VSO in declarative sentences, it always puts interrogative words or phrases first in interrogative word questions; if it has dominant order SOV in declarative sentences, there is never such an invariant rule." Many SVO languages have overt wh-movement too, such as English, but some do not, such as Chinese. Languages with no overt wh-movement are referred to as wh-in-situ languages. In 1981, Huang argued[2] that there must in fact be wh-movement in Chinese, though this movement is covert and unpronounced. His arguments were widely influential for theories of generative grammar.[3]
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English is one language that features wh-movement. For example, a declarative sentence in English featuring normal word order would be:
The direct object, "bread", of the verb, "buy", normally follows the verb; however, when the direct object is replaced with a wh-word in order to form a question, the wh-word generally appears at the beginning of the sentence:
In standard English main clause questions in which the question word is not the subject, an auxiliary verb needs to follow a wh-word. If there is no auxiliary verb, a form of the auxiliary "do" must be used. The auxiliary verb occurs after the wh-word and before the subject:
A question word can also serve as the subject, which is normally at the beginning of a declarative main clause. The question-word subject stays at the front.
There are three circumstances in which wh-movement does not occur in English (aside from when the question word serves as the subject and so is already fronted): echo questions (to confirm what you thought you heard), quiz questions, and multiple questions, when there is already one wh-word at the front:
Wh-movement is also seen in subordinate clauses in English. Sentences of the kind below are sometimes called embedded (or indirect) questions.
rather than
However, most varieties of English do not show the auxiliary do in such cases:
In most varieties of English, other auxiliaries remain in their normal position after the subject of the sentence:
rather than
Belfast English has been cited as an example of an English dialect where *I wonder what did he buy and *I wonder what should he buy are allowed. However, most North American and British English disallows these constructions.
Examples like this demonstrate that the wh-phrase does not necessarily occur at the front of the sentence, but sometimes occurs at the beginning of a subordinate clause. However, sometimes wh-movement can extend over several clauses all the way to the front of the sentence. In the following example, the fronted question word what is the object of the verb buys in the third clause, which is a dependent clause:
To see the extent of the movement, note that in the absence of fronting the word order would have been as in She thinks that I said that he buys what?
Wh-words used in relative clauses can also be moved to the front of the clause:
In these examples the wh-word may be omitted:
The word that may also be used instead of a wh-word in this context:
The name wh-movement comes from analyses in Generative Grammar where a wh-word begins at some other place in a sentence and moves to the front. Although wh-movement is a common name for this phenomenon, there are also a number of other elements in a sentence that show the special word order found in questions.
The details of wh-movement are very complex, particularly when English is compared to other languages with wh-movement. All modern theories of syntax have some part of the theory which deals with the correct formulation of the rules for wh-movement.
Because of debate about the best analysis of wh-movement, there is also some variation in the terminology for talking about the parts of a sentence that contains wh-movement. However, any theory will need to talk about all of the following:
In early transformational approaches to syntax, the analysis of wh-movement involved two syntactic levels -- deep structure and surface structure. The moved element occupies the position of the "gap" at deep structure. It undergoes a rule which moves it to a special position at the beginning of a clause. The structure of the sentence after the movement rule is called surface structure. In more modern approaches to syntax such as Minimalism, there is no special deep structure level, but words and phrases still undergo movement to arrive at their final position.
Theories that do not posit separate syntactic levels like deep structure and surface structure, such as lexical-functional grammar and head-driven phrase structure grammar, do not use movement rules as such in their analyses. Instead they speak of the dependency relationship between the "filler" and the "gap" in a sentence to account for the grammar of these sentences through restrictions on the feature structures on the sentences.
Wh-movement is also found in many other languages around the world. Most European languages also place wh-words at the beginning of a clause, as in the following Spanish example:
| ¿Qué | compró | Juan? |
| what | bought | Juan |
'What did Juan buy?'
In this example qué is the object of the verb compró, but it appears at the beginning of the interrogative clause. In contrast, a normal object will follow the verb:
| Juan | compró | carne. |
| Juan | bought | meat. |
'Juan bought meat.'
Wh-movement is also found in many other languages around the world. In some languages, such as French, it is optional in certain matrix clauses.[4]
Pied-piping (first identified by John R. Ross) describes the situation where a phrase larger than a single wh-word occurs in the fronted position. In the case where the wh-word is a determiner such as which or whose, pied-piping refers to the wh-determiner's appearance sentence-initially along with its complement. For instance, in the following example, the entire phrase "which car" is moved:
In the transformational analysis, the wh-word which moves to the beginning of the sentence, taking car, its complement, with it, much as the Pied Piper of Hamelin attracted rats and children to follow him, hence the term pied-piping.
In the case of determiners, pied-piping is obligatory. For instance, the following sentence would be ungrammatical:
However, there are cases where pied-piping can be optional. In English, this is often the case when a wh-word or phrase is the object of a preposition. For instance, the following two examples are both grammatical:
The second example is a case of preposition stranding, which is possible in English, but not allowed in Latin or other Romance languages. For languages that use postpositions rather than prepositions, stranding is not allowed either.
Prescriptive grammarians often claim that preposition stranding should be avoided in English as well; however, in certain contexts obligatory pied-piping of prepositions in English may make a sentence feel artificial or stilted (e.g. "To whom are you talking?" rather than the more conventional "Who are you talking to?").
Some languages show a special word order in pied-piped phrases. This phenomenon is known as pied-piping with inversion or secondary wh-movement.
In many cases, a wh-word can occur at the front of a sentence, regardless of how far away its canonical location is. For example:
In more technical terms, we can say that the dependency relation between the gap and its filler is unbounded in the sense that there is no upper bound on how deeply embedded within the given sentence the gap may appear. Consider the following three examples:
In these examples, the NP the book functions as a filler and a gap in the embedded clause. As shown above, there is no grammatical limit on how many layers of embedding there should be to make a grammatical sentence. (If we don't attempt a much longer sentence with the embedding structure, that's probably because of processing constraints or psychological reasons, not because of the grammatical restriction of the long-distance dependencies.)
However there are cases in which this is not possible. Certain kinds of phrases do not seem to allow a gap. These phrases from which a wh-word cannot be extracted are referred to as extraction islands or simply islands. In addition to the islands listed below, regular that-clauses serving as complements to verbs may show island-like behavior if the matrix verb is not a so-called bridge verb (a verb permitted movement across it, hence the name, coined in Erteschik-Shir 1973). Non-bridge verbs include manner-of-speaking verbs, such as whisper or shout. Compare (the star indicates that the sentence is not acceptable):
An adjunct island is a type of island formed from an adjunct clause. Wh-movement is not possible out of an adjunct clause. Adjunct clauses include clauses introduced by because, if, and when, as well as relative clauses. Some examples include:
A wh-island is an island that is created by an embedded sentence which is introduced by a wh-word. For instance, the clause "where Eric went to buy the gift" in the following example, is a wh-island:
Wh-islands are weaker than adjunct islands since extraction is often awkward but not necessarily considered ungrammatical by all speakers.
It is typically easier to extract objects rather than subjects from a clause, especially when an overt complementizer such as "that" or "for" is used. Take the following examples:
Wh-movement does not appear to be possible out of phrases that appear in the subject position. This is particularly true for subject clauses. For instance, here is a sentence where the clause appears in a non-subject position (the predicative complement):
Here is the same sentence where the clause appears in the subject position:
Notice that wh-movement can occur only in the clause that appears in the predicate position:
The left branch of an NP cannot be extracted.[5]
Two subcases fall under this ban: attributive adjectival phrases (and their subparts) and possessors:
In these situations, pied-piping is obligatory.
Left branch islands are among the most cross-linguistically variable; while they exist in English, they are absent in many other languages (most famously, the Slavic languages).[6]
Extraction out of a conjunct is possible only if this extraction affects all conjuncts equally (that is, if it occurs in an across-the-board manner):
Extraction out of complex noun phrase such as [a man who went on holiday] is ungrammatical: