Subject–auxiliary inversion involves placing the subject after a finite auxiliary verb,[2] rather than before it as is the case in typical declarative sentences (the canonical word order of English being subject–verb–object).
A typical example of subject–auxiliary inversion is: Here the subject is Sam, and the verb has is an auxiliary.
If the sentence does not have an auxiliary verb, this type of simple inversion is not possible.
Instead, an auxiliary must be introduced into the sentence in order to allow inversion:[3] For details of the use of do, did and does for this and similar purposes, see do-support.
In this case the subject remains before the verb (it can be said that wh-fronting takes precedence over subject–auxiliary inversion): Inversion also does not normally occur in indirect questions, where the question is no longer in the main clause, due to the penthouse principle.
Examples of non-auxiliary verbs being used in typical subject–auxiliary inversion patterns may be found in older texts or in English written in an archaic style: The verb have, when used to denote broadly defined possession (and hence not as an auxiliary), is still sometimes used in this way in modern standard English: In some cases of subject–auxiliary inversion, such as negative inversion, the effect is to put the finite auxiliary verb into second position in the sentence.
In these cases, inversion in English results in word order that is like the V2 word order of other Germanic languages (Danish, Dutch, Frisian, Icelandic, German, Norwegian, Swedish, Yiddish, etc.).
[citation needed] These instances of inversion are remnants of the V2 pattern that formerly existed in English as it still does in its related languages.
[5] An alternative analysis does not acknowledge the binary division of the clause into subject NP and predicate VP, but rather it places the finite verb as the root of the entire sentence and views the subject as switching to the other side of the finite verb.