Syntactic movement is the means by which some theories of syntax address discontinuities. Movement was first postulated by structuralist linguists who expressed it in terms of discontinuous constituents or displacement. Certain constituents appear to have been displaced from the position where they receive important features of interpretation. The concept of movement is controversial; it is associated with so-called transformational or derivational theories of syntax (e.g. Transformational Grammar, Government and Binding Theory, Minimalist Program). Representational theories (e.g. Head-Driven Phrase Structure Grammar, Lexical Functional Grammar, Construction Grammar, most dependency grammars), in contrast, reject the notion of movement, often addressing discontinuities in terms of feature passing instead.
- a. John has told Peter that Mary likes the first story.
- b. Which story has John told Peter that Mary likes ___? - Wh-fronting
- a. We want to hear that one story again.
- b. That one story we want to hear ___ again. - Topicalization
- a. Something that we weren't expecting occurred.
- b. Something ___ occurred that we weren't expecting. - Extraposition
- a. You will understand.
- b. Will you ___ understand? - Inversion
- a. She took off her hat.
- b. She took her hat off ___. - Shifting
The a-sentences show canonical word order, and the b-sentences illustrate the result of movement. Bold script marks the expression that is moved, and the blanks mark the positions out of which movement is assumed to have occurred. Each time, movement takes place in order to focus or emphasize the expression in bold. For instance, the constituent which story in the first b-sentence is the object of the transitive verb likes, the canonical position of an object being immediately to the right of the verb. By fronting the object as a wh-expression, it becomes the focus of communication.
The representation of movement 
The examples above use a blank to mark the position out of which movement is assumed to have occurred. Blanks are just one means of indicating movement, however. Two other means are traces and copies. In transformational grammar, movement has been signaled by a trace t since at least the 1970s proposal by Noam Chomsky, e.g.
- b. Which story1 has John told Peter that Mary likes t1? - Movement indicated using a trace
Subscripts help indicate the constituent that is assumed to have left a trace in its former position, the position marked by t. The other means of indicating movement is in terms of copies. Movement is actually taken to be a process of copying the same constituent in different positions, deleting the phonological features in all but one case. Italics are used in the following example to indicate a copy that lacks phonological representation:
- b. Which story has John told Peter that Mary likes which story? - Copy indicated using italics
While there are various nuances associated with each of these means of indicating movement (blanks, traces, copies), for the most part, each convention has the same goal, which is to indicate the presence of a discontinuity.
Types of movement 
Within generative grammar, various types of movement have been discerned. Two important distinctions are A-movement vs. A-bar movement and phrasal vs. head movement.
A-movement vs. A-bar movement 
Argument movement (A-movement) displaces a phrase into a position where a fixed grammatical function is assigned, such as in movement of the object to the subject position in passives:
- a. Fred read the book.
- b. The book was read ___ (by Fred). - A-movement
Non-argument movement (A-bar movement or A'-movement), in contrast, displaces a phrase into a position where a fixed grammatical function is not assigned, such as movement of a subject or object NP to a pre-verbal position in interrogatives:
- a. You think Fred loves Mary.
- b. Who do you think ___ loves Mary? - A-bar movement
- a. You think Fred loves Mary.
- b. Who do you think Fred loves ___? - A-bar movement
The A- vs. A-bar distinction is a reference to the theoretical status of syntax with respect to the lexicon. The distinction elevates the role of syntax, locating the theory of voice (active vs. passive) almost entirely in syntax (as opposed to in the lexicon). A theory of syntax that locates the active-passive distinction in the lexicon - i.e. the passive is not derived via transformations from the active - will reject the distinction entirely.
Phrasal movement vs. head movement 
A different partition among types of movement is phrasal vs. head movement. Phrasal movement occurs when the head of a phrase moves together with all its dependents in such a manner that the entire phrase moves. Most of the examples above involve phrasal movement. Head movement, in contrast, occurs when just the head of a phrase moves, whereby this head leaves behind its dependents. Subject-auxiliary inversion is a canonical instance of head movement, e.g.
- a. Someone has read the article.
- b. Has someone ___ read the article? - Head movement of the auxiliary verb has
- a. She will read the second article.
- b. Will she ___ read the second article? - Head movement of the auxiliary verb will
On the assumption that the auxiliaries has and will are the heads of phrases - of IPs (inflection phrases), for instance - the b-sentences are the result of head movement, whereby the auxiliary verbs has and will move leftward without taking with them the rest of the phrase that they head.
The distinction between phrasal movement and head movement relies crucially on the assumption that movement is occurring leftward. An analysis of subject-auxiliary inversion that acknowledges rightward movement can dispense with head movement entirely, e.g.
- a. Someone has read the article.
- b. ___ Has someone read the article? - Phrasal movement of the subject pronoun someone
- a. She will read the second article.
- b. ___ Will she read the second article? - Phrasal movement of the subject pronoun she
The analysis shown in these sentences sees the subject pronouns someone and she moving rightward (instead of the auxiliary verbs moving leftward). Since these pronouns lack dependents, i.e. they alone qualify as complete phrases, there would be no reason to assume head movement.
Islands and barriers to movement 
Since it was first proposed, the theory of syntactic movement yielded a new field of research aiming at providing the filters that block certain types of movement, also called locality theory. Locality theory is interested in discerning the islands and barriers to movement. It strives to identify the categories and constellations that block movement from occurring. In other words, one wants to understand why certain attempts at movement fail, e.g.
- a. You think that Mary visited Peter before calling Fred.
- b. *Who do you think that Mary visited Peter before calling ___? - Attempt fails to move Fred/who out of the adjunct before calling Fred.
- a. Your picture of Fred was funny.
- b. *Who was your picture of ___ funny? - Attempt fails to move Fred/who out of the subject NP your picture of Fred.
- a. You like Bill's ideas.
- b. *Whose do you like ___ ideas? - Attempt fails to move Bill's/whose out of the object NP Bill's ideas.
The b-sentences are now all disallowed due to locality constraints on movement. Adjuncts and subjects are islands that block movement, and left branches in NPs are barriers that prevent pre-noun modifiers from being extracted out of NPs.
Feature passing 
Syntactic movement is controversial, especially in light of movement paradoxes. Theories of syntax that posit feature passing reject syntactic movement outright, that is, they reject the notion that a given "moved" constituent ever appears in its "base" position below the surface, i.e. the positions marked by blanks, traces, or copies. Instead, they assume that there is but one level of syntax, whereby all constituents only ever appear in their surface positions - there is no underlying level or derivation. To address discontinuities, they posit that the features of a displaced constituent are passed up and/or down the syntactic hierarchy between that constituent and its governor. The following tree illustrates the feature passing analysis of a wh-discontinuity in a dependency grammar:
The words in red mark the catena (chain of words) that connects the displaced wh-constituent what to its governor eat, the word that licenses its appearance. The assumption is that features (=information) associated with what (e.g. noun, direct object) are passed up and down along the catena marked in red. In this manner, the ability of eat to subcategorize for a direct object NP is acknowledged. By examining the nature of catenae like the one in red here, the locality constraints on discontinuities can be identified.
See also 
- Concerning the terminology of movement, see Graffi (2001).
- Concerning the interpretation of features as the motivation for movement, see Carnie (2013:393ff.).
- See for instance Roberts (1997:35f.) and Haegeman and Guéron (1999:32) for an introduction to the concept of movement.
- See Chomsky (1975) for an early example of the use of traces to mark movement.
- For examples of t used in this manner, see for instance Ouhalla (1994:63) and Haegeman and Guéron (1999:172).
- See Chomsky (1995) concerning the copy theory of movement.
- See for instance Ouhalla (1994:161f.) and Radford (2004:176ff.) concerning the distinction between A- and A-bar positions.
- Concerning head movement, see for instance Ouhalla (1994:284f.), Radford (2004:123ff.) and Carnie (2013:289ff.).
- See Manzini (1992) for illustrations of different types of locality theories.
- For the dependency grammar analysis of discontinuities in terms of feature passing and catenae, see Osborne et al. (2012).
- Carnie, A. 2013. Syntax. A generative introduction. 3rd edition. Oxford, England: Blackwell.
- Chomsky, N. 1975. Reflections on Language. New York: Pantheon Books.
- Chomsky, N. 1995. The minimalist program. Cambridge, MA: The MIT Press.
- Haegeman, L. and J. Guéron. 1999. English grammar: A generative perspective. Oxford, UK: Blackwell Publishers.
- Graffi, G. 2001. 200 Years of Syntax: A critical survey. Amsterdam: John Benjamins.
- Manzini, R. 1992. Locality, Linguistic Inquiry Monograph Series 19. Cambridge, MA: The MIT Press.
- Osborne, T., M. Putnam, and T. Groß 2012. Catenae: Introducing a novel unit of syntactic analysis. Syntax 15, 4, 354-396.
- Ouhalla, J. 1994. Introducing transformational grammar: From principles and parameters to minimalism. London: Arnold.
- Radford, A. 2004. English syntax: An introduction. Cambridge, UK: Cambridge University Press.
- Robers, I. 1997. Comparative syntax. London: Arnold.