Concept
In syntax, shifting occurs when two or more constituents appearing on the same side of their common head exchange positions in a sense to obtain non-canonical order. The most widely acknowledged type of shifting is heavy NP shift, but shifting involving a heavy NP is just one manifestation of the shifting mechanism. Shifting occurs in most if not all European languages, and it may in fact be possible in all natural languages including sign languages. Shifting is not inversion, and inversion is not shifting, but the two mechanisms are similar insofar as they are both present in languages like English that have relatively strict word order. The theoretical analysis of shifting varies in part depending on the theory of sentence structure that one adopts. If one assumes relatively flat structures, shifting does not result in a discontinuity. Shifting is often motivated by the relative weight of the constituents involved. The weight of a constituent is determined by a number of factors: e.g., number of words, contrastive focus, and semantic content. Shifting is illustrated with the following pairs of sentences. The first sentence of each pair shows what can be considered canonical order, whereas the second gives an alternative order that results from shifting: I gave the books which my uncle left to me as part of his inheritance to her. I gave to her the books which my uncle left to me as part of his inheritance. The first sentence with canonical order, where the object noun phrase (NP) precedes the oblique prepositional phrase (PP), is marginal due to the relative 'heaviness' of the NP compared to the PP. The second sentence, which shows shifting, is better because it has the lighter PP preceding the much heavier NP. The following examples illustrate shifting with particle verbs: He picked it up. (compare: *He picked up it.) He picked up the flashlight. John took him on. (compare: *John took on him.) John took on the new player. When the object of the particle verb is a pronoun, the pronoun must precede the particle, whereas when the object is an NP, the particle can precede the NP.