Extraposition in Grammar

Glossary of Grammatical and Rhetorical Terms

Sentence (b) is an example of extraposition--and, in contemporary English, a far more common construction than sentence (a).

An extraposition is a construction (or transformation) in which a clause that acts as a subject is moved (or extraposed) to the end of the sentence and replaced by dummy it in the initial position. Also known as rightward movement.

In certain cases extraposition of a modifying clause is prohibited. In other cases, with a small set of verbs (including appear, happen, and seem), extraposition is obligatory.

An extraposed subject is sometimes called a postponed subject.

Examples and Observations

  • It is obvious that you have been misled.
  • It's a shame what happened to you and your sister.
  • It might be a good idea to wear a respirator mask when you're working with fiberglass.
  • "It's likely that the enemy simply dropped back off the hilltop once they'd grabbed all the weapons they could carry."
    (Sebastian Junger, War. Twelve, 2010)
  • It surprised everybody that Marlene had so much energy and strength.

Extraposition and the End-Weight Principle

"Certain types of long subject clauses are usually avoided in English because they violate the end-weight principle, and sound awkward. Finite that-clauses, wh-nominal clauses and to-infinitive clauses can all be shifted to the end of the sentence and replaced by 'anticipatory it' in subject position.

Clause as Subject
(a) That the banks are closed on Saturday is a nuisance.
(b) What they are proposing to do is horrifying.
(c) To interfere would be unwise.

Extraposed Clause
(a) It's a nuisance that the banks are closed on Saturday.
(b) It's horifying what they are proposing to do.
(c) It would be unwise to interfere.

Extraposed clauses are much preferred in English to the non-extraposed, as they sound much less awkward. The reason for is that they satisfy the principles of end-weight and end-focus, thus 'packaging' the information in a way that is easier to process."
(Angela Downing, English Grammar A University Course.

Routledge, 2006)

Extraposition and English Word Order

"There is a tendency in English not to like heavy elements, such as clauses, at the beginning of a sentence, but to prefer them at the end. This preference is a result of the basic Su-V-O structure of English, where objects are typically longer than subjects. Thus, . . . while sentence (1) That coffee grows in Brazil is well known to all . . . is perfectly grammatical, it is much more natural to use the synonymous sentence (7) It is well known that coffee grows in Brazil.

"Because sentences (1) and (7) are synonymous and because the that-clause is logically functioning as subject in both sentences, we will derive sentence (7) from sentence (1) by a rightward movement transformation called extraposition. Such a transformation moves an element to an 'extra' or added 'position' at the end of the sentence. When the clause is extraposed, the original subject position, which is an obligatory position in the sentence that cannot be deleted, is filled by a 'dummy' place-holder, anticipatory it; it has no lexical meaning here, but serves merely as a structural device."
(Laurel J. Brinton and Donna M. Brinton, The Linguistic Structure of Modern English.

John Benjamins, 2010)

Extraposition vs. Clarification

  • "Extraposition shifts a unit to the end of the clause (except that certain peripheral adjuncts may still follow it) and inserts it into the vacated position. The construction is to be distinguished from that exemplified in
    (12) They're excellent company, the Smiths.
    Here the Smiths has something of the character of an afterthought; its function is to clarify the reference of the personal pronoun they."
    (Rodney Huddleston, Introduction to the Grammar of English. Cambridge University Press, 1984)

Extraposition of Subject Complements

"For Extraposition of subject complements, the form of the V' is immaterial, subject to the qualification the Extraposition is avoided when it gives rise to certain awkward combinations that are generally avoided. For example, if there is both a subject complement and an object complement, extraposition of the subject complement gives rise to a derived structure in which the object complement is in the middle of the sentence:

(6a) That the corkscrew had blood on it proves that the butler is the culprit.
(6a') *It proves that the butler is the culprit that the corkscrew had blood on it.

Sentences having a S in the middle of a constituent are avoided regardless of whether Extraposition plays any role in them . . .."
(James D. McCawley, The Syntactic Phenomena of English, 2nd ed. University of Chicago Press, 1998)