5.5: Clausal embedding

Recursion: Sentences inside sentences

So far we’ve talked about the organization of words into constituents in a single clause. Consider the sentence in (1), which we saw before in 6.4 Identifying phrases: Constituency tests:

(1) The students saw a movie about dinosaurs.

This sentence has 3 noun phrases: [the students], [dinosaurs], and [a movie about dinosaurs]. The noun phrase [dinosaurs] is inside the bigger constituent [a movie about dinosaurs], and they’re linked together by a preposition about—in fact, [about dinosaurs] is a prepositional phrase. We also have a verb phrase [saw a movie about dinosaurs]—the verb and its object (or its objects, if it is ditransitive), will always be part of the same verb phrase constituent. Now consider the sentences in (2) and (3):

(2) Deniz said something.
(3) Samnang might leave.

In (2), the object of the verb said is something; together these form a verb phrase. But now consider a sentence like (4):

(4) Deniz said that [ Samnang might leave ].

In (4), the entire clause from (3) appears after the verb said, in the same position that something appeared in (2). Also, if we do constituency tests—for example replacement in (5)—we can see that [said that Samnang might leave] is a verb phrase that can be replaced by do (too).

(5) Keiko said that Samnang might leave, and Deniz did too.

What we see here is that the complement of a verb can be a whole clause; in this case we call the clause-inside-a-clause an embedded clause. What about the word that? The role of that seems to be to introduce the embedded clause. Words that have this function of introducing an embedded clause belong to the category complementizers (called that because they turn clauses into the complements of verbs). Like other categories, complementizers create complementizer phrases (CPs). Here the complementizer phrase is [ that Samnang might leave ]; again, you can identify this constituent with tests.

(6) It was that Samnang might leave that Deniz said __.

Just as verbs select how many complements they take, they can also select the category of their complement. Some transitive verbs can combine only with noun phrase objects, some only with prepositional phrases, some only with complementizer phrases—and some with any or all of these. For example, the verb know can combine with several different categories of complements:

(7) They know…
…this fact. (noun phrase)
…about birds. (prepositional phrase)
…that birds can fly. (complementizer phrase)
Other verbs can only take some of these as complements:
(8) We ate…
…curry. (noun phrase)
*…about curry. (*prepositional phrase)
*…that curry is for dinner. (*complementizer phrase)
(9) The teacher said…
…something. (noun phrase)
*…about chocolate. (*prepositional phrase)
…that they like chocolate. (complementizer phrase)
(10) They talked…
…mythology. (noun phrase)
…about mythology. (prepositional phrase)
*…that mythology is interesting. (*complementizer phrase)

(Some people might not find They talked mythology. totally grammatical; whether talk can take a noun phrase object is something that has changed over time in English.) So far the examples of embedded clauses that we’ve seen are all embedded statements. Is that the only kind of embedded clause that exists in English, or in language in general? Are there any complementizers other than that? Take a moment to see if you can think of some other verbs that embed whole clauses, and see if you can identify some element in those sentences that looks like another complementizer. You can do this for English, or for another language that you know.

Questions inside sentences: Embedded interrogative clauses

We just saw that the English verb know can combine with several different types of complements (complementizer phrases, noun phrases, and prepositional phrases). It also happens to be able to combine with more than one type of embedded clause. Consider the following examples:

(11) I know…
…(that) ghosts exist.
whether ghosts exist.
if ghosts exist.

What we see here is that the verb know can combine not only with clauses introduced by that (or nothing), but also ones introduced by whether or if. Another way to write this would be to use < curly braces >to surround the complementizers allowed after know, as in:

(12) I know [CP ghosts exist ].

Not all verbs are equally flexible! Some verbs, like believe, only allow that or ∅, not whether or if:

(13) a. I believe [CP ghosts exist ].̱
b. *I believe [CP ghosts exist ].̱
Other verbs only allow whether or if as complementizers, like wonder:
(14) a. *I wonder [CP ghosts exist ].̱
b. I wonder [CP ghosts exist ].

What this tells us is that the difference between that or ∅ on the one hand, and whether or if on the other hand, is something that verbs can be sensitive to when it comes to selection. What, then, is the difference between these two sets of complementizers? We can see the difference if we look at their use with verbs of quotation, comparing embedded clauses with direct quotation (indicated in English writing by using quotation marks). Consider the verb say in (15):

(15) They said that ghosts exist. = They said: “Ghosts exist.

The embedded clause introduced by that can directly paraphrase a directly quoted statement. Now compare the verb ask in (16):

(16) They asked if ghosts exist. = They asked: “Do ghosts exist?