Inversion (grammar)

In linguistics, inversion is any of several grammatical constructions where two expressions switch their canonical order of appearance, that is, they invert. The most frequent type of inversion in English is subject–auxiliary inversion in which an auxiliary verb changes places with its subject; it often occurs in questions, such as Are you coming?, with the subject you is switched with the auxiliary are. In many other languages, especially those with a freer word order than English, inversion can take place with a variety of verbs (not just auxiliaries) and with other syntactic categories as well.

When a layered constituency-based analysis of sentence structure is used, inversion often results in the discontinuity of a constituent, but that would not be the case with a flatter dependency-based analysis. In that regard, inversion has consequences similar to those of shifting.

In broad terms, one can distinguish between two major types of inversion in English that involve verbs: subject–auxiliary inversion and subject–verb inversion. The difference between these two types resides with the nature of the verb involved: whether it is an auxiliary verb or a full verb.

The most frequently occurring type of inversion in English is subject–auxiliary inversion. The subject and auxiliary verb invert (switch positions):

The default order in English is subject–verb (SV), but a number of meaning-related differences (such as those illustrated above) motivate the subject and auxiliary verb to invert so that the finite verb precedes the subject; one ends up with auxiliary–subject (Aux-S) order. That type of inversion fails if the finite verb is not an auxiliary:

(The star * is the symbol used in linguistics to indicate that the example is grammatically unacceptable.)

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