According to Joseph Greenberg's linguistic universal No.12, VSO languages always have wh-movement, while SOV languages never do. Many SVO languages have wh-movement too, such as English, but some don't, such as Chinese. Languages without wh-movement are referred to as wh-in-situ languages.
In standard English main clauses, an auxiliary verb needs to follow a wh-word. If there is no auxiliary verb, a form of "do" must be used. The auxiliary verb (or a form of "do") occurs after the wh-word and before the subject:
As mentioned above, wh-movement can extend over several clauses. Note the following example:
The subject, which is normally at the beginning, can also be questioned. The question word also goes at the front, replacing the subject. There does not seem to be any movement here, but for uniformity of explanation it may be that there is also movement and a trace here too:
There are three circumstances when wh-movement does not occur in English: echo questions (to confirm what you thought you heard), quiz questions, and 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 questions.
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:
Examples like this show us that the wh-phrase does not necessarily occur at the front of the sentence, but sometimes occurs at the beginning of a subordinate clause.
Belfast English has been cited as 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.
Wh-words at the front of the clause are also seen in relative clauses in English:
In some of these examples the wh-word may be omitted:
The word that may also be used instead of a wh-word:
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, wh-movement is probably not the best name because there are 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 disagreement about the best analysis of wh-movement, there is also some disagreement about the terminology for talking about the parts of a sentence that contains wh-movement. However, any theory will need to talk about
a.) the word or phrase which shows a special order, usually at the beginning of a clause. This word or phrase is sometimes called the filler or the moved element. b.) the position where the word or phrase would normally have appeared. This position is often called the gap, and in some theories of syntax there is a silent element called the trace , which occupies this position. The trace is sometimes indicated in a syntactic diagram of the sentence as t (for trace) or e (for empty). c.) the part of the sentence which is between the "filler" and the "gap". This part of the sentence is sometimes called the "dependency path".
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 which reject deep structure and surface structure, such as lexical-functional grammar and head-driven phrase structure grammar, do not use movement rules in their analyses. Instead they speak of the dependency relationship between the "filler" and the "gap" in a sentence and try to account for the grammar of these sentences through restrictions on the feature structures on the sentences.
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.
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:
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:
Wh-movement is also found in many other languages around the world. In some languages, it is optional. Languages with optional wh-movement include Portuguese.
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 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:
: This is the book [which [John recommended ____ t ]].
: This is the book [which [I think [John recommended ___t ]]].
: This is the book [which [I think [you said [John recommended ___t ]]]].
In these examples, the NP the book functions as a filler 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 the processing constraints or the psychological reason, 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.
Wh-islands are weaker than adjunct islands since extraction is often awkward but not necessarily considered ungrammatical by all speakers.
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: