As a syntactic head, C always
selects for a complement tense phrase (TP) whose syntax and semantics are dictated by the choice of C. The choice of C can determine whether the associated TP is finite or non-finite, whether it carries the semantic meaning of certainty or uncertainty, whether it expresses a question or an assertion, etc.
Propositions vs. indirect questions The following complementizers are available in English:
that, for, if, whether, ∅.
If and
whether form CPs that express
indirect questions: :
John wonders whether / if it is raining outside. In contrast, the complementizers
for, that, as well as the phonologically null complementizer
∅, introduce "
declarative or non-interrogative" CPs. :
John thinks ∅ it is raining outside. :
John thinks that it is raining outside. :
John prefers for it to be raining. Finite vs. non-finite TPs Tense phrases in English can be divided into finite (tensed) clauses or non-finite (tenseless) clauses. The former includes an indication of the relative time when its content occurs; the latter has no overt indication of time. Compare
John will leave (John's leaving will take place in the future) with
John wants to leave (we are unsure when John is leaving). Certain complementizers strictly select for finite clauses (denoted [+finite]) while others select for non-finite clauses (denoted [-finite]). Complementizers
if, that require [+tense] TP: :
Mary wishes that she will win the game. (future) :
Mary believes if she wins the game, she can date John. (present) Complementizer
for requires a [-tense] TP: :
Mary hopes for Kate to win the game. (infinitive) Complementizer
whether allows either [+tense] or [-tense] TP: :
John wonders whether Mary will win the game. (future) :
Mary wonders whether to win the game or not. (infinitive)
Epistemic selection Complementizers frequently carry
epistemic meaning about the speaker's degree of certainty, such as whether they are doubtful, or the speaker's source of information, such as whether they are making an inference or have direct evidence. Contrast the meaning of "if" and "that" in English: :''John doesn't know
if Mary is there.'' :''John doesn't know
that Mary is there.'' "If" signals that the associated tense phrase must carry the epistemic meaning of uncertainty. In contrast, "that" is epistemically neutral. The contrast is not uncommon cross-linguistically. In languages with only two complementizers, one is frequently neutral, and the other carries the meaning of uncertainty. One such language is
Lango (a Nilotic language spoken in Uganda): Additional languages with the neutrality/uncertainty complementizer contrast include several European languages: In other languages, complementizers are richer in epistemic meaning. For example, in
Mbula, an Austronesian language of Papua New Guinea, the following complementizers are available: More generally, complementizers have been found to express the following values cross-linguistically: certainty, (general) uncertainty, probability, negative probability/falsehood, apprehension, and reportativity. Complementizers in Itzaj Maya also demonstrate epistemic meaning. For instance, English
that and Itzaj Maya are used not only to identify complements but also to introduce relative clauses: (1a) introduces a subordinate clause and (1b) introduces a conditional clause, similar to English. The former subtype
that can be defined in terms of
information source and includes meanings glossed as direct evidence, indirect evidence, hearsay, inferential. The latter subtype
if can be defined in terms of
degree of certainty and includes meanings glossed as certainty, probability, epistemic possibility, doubt. Thus, epistemic meaning as a whole can be defined in terms of the notion of
justificatory support.
Complementizer stacking Itzaj Maya can even combine the neutral complementizer, , with the non-neutral, , as is illustrated in examples (2a) in which the neutral complementizer occurs alone and (2b) in which it is optionally inserted in front of the uncertainty complementizer : In (1a,b) and (2a), each complementizer can be licensed once within the clause, but in (2b), the significant difference of Itzaj Maya from English is observed. English can license multiple C as long as the clause is completed with the embedded V or D. For example, I saw that fox that ran towards the garden that Tommy took care of. In such cases, C can appear as the complement of V or D many times. However, CP-recursion in two tiers or CP appearing as an immediate complement of maximal projection CP cannot be allowed in English. That action of
Complementizer Stacking is realised as ungrammatical. In Scandinavian languages, however, the phenomenon of complementizer stacking occurs. For example, researchers observed the two basic types of CP-recursion that occur independently in Danish: a CP with V2 (i.e. a CP headed by a lexical predicate in its head position) will be referred as CP ("big CP"), and a CP without V2 (i.e. CP headed by a non-lexical element) will be referred to as cP ("little cP"). • [cP c° [– LEXICAL ("little cP") • [cP [+ LEXICAL ("big CP") The case of little/big CPs are comparable to the "VP shell" structure in English, which introduces a small
v in the higher position in the tree and big
V in the lower position in the tree. In the examples, Danish also allows complementizer stacking in constructions involving subject extraction from complement and relative clauses in colloquial speech: {{Interlinear |lang=da |number=(3) a. |abbreviations=REL:relative clauses Complementizers are indeed stacked together in the beginning of the clause and act as a complement of DP. CP-recusion structure on the right is applied for each of the clause, which points to evidence of complementizer stacking in Danish. In addition, the combination of
som at der in (3a) is possible in only one specific order, which led the researchers to believe that s
om may not require an empty operator in its Spec-CP position. ==In various languages==