In linguistics (especially generative grammar), complementizer or complementiser (glossing abbreviation: comp) is a functional category (part of speech) that includes those words that can be used to turn a clause into the subject or object of a sentence. For example, the word that may be called a complementizer in English sentences like Mary believes that it is raining. The concept of complementizers is specific to certain modern grammatical theories; in traditional grammar, such words are normally considered conjunctions.

The standard abbreviation for complementizer is C. The complementizer is often held to be the syntactic head of a full clause, which is therefore often represented by the abbreviation CP (for complementizer phrase). Evidence that the complementizer functions as the head of its clause includes that it is commonly the last element in a clause in head-final languages like Korean or Japanese, in which other heads follow their complements, whereas it appears at the start of a clause in head-initial languages such as English, where heads normally precede their complements.[citation needed]

Types and developmentEdit

It is common for the complementizers of a language to develop historically from other syntactic categories (a process known as grammaticalization). Across the languages of the world, it is especially common for pronouns or determiners to be used as complementizers (e.g., English that). Another frequent source of complementizers is the class of interrogative words. It is especially common for a form that otherwise means what to be borrowed as a complementizer, but other interrogative words are often used as well; e.g., colloquial English I read in the paper how it's going to be cold today, with unstressed how roughly equivalent to that. English for in sentences like I would prefer for there to be a table in the corner shows a preposition that has arguably developed into a complementizer. (The sequence for there in this sentence is not a prepositional phrase under this analysis.) In many languages of West Africa and South Asia, the form of the complementizer can be related to the verb say. In these languages, the complementizer is also called the quotative. The quotative performs many extended functions in these languages.

Empty complementizersEdit

Some analyses allow for the possibility of invisible or "empty" complementizers. An empty complementizer is considered to be present when there is not a word, even though the rules of grammar expect one. The complementizer (for example, "that") is usually said to be understood – i.e., an English speaker knows it is there, and so it does not need to be said. Its existence in English has been proposed based on the following type of alternation:

He hopes you go ahead with the speech
He hopes that you go ahead with the speech

Because that can be inserted between the verb and the embedded clause without changing the meaning, the original sentence without a visible complementizer would be reanalyzed as

He hopes øC you go ahead with the speech

Where the symbol øC represents the empty (or "null") complementizer, this suggests another interpretation of the earlier "how" sentence:

I read in the paper <how> øC [it's going to be cold today]

where "how" serves as a specifier to the empty complementizer. This allows for a consistent analysis of another troublesome alternation:

The man <whom> øC [I saw yesterday] ate my lunch!
The man <OP> øC [I saw yesterday] ate my lunch!
The man <OP> that [I saw yesterday] ate my lunch!

where "OP" represents an invisible interrogative known as an operator.

In a more general sense, the proposed empty complementizer parallels the suggestion of near-universal empty determiners.

In various languagesEdit

Assyrian Neo-AramaicEdit

In Assyrian Neo-Aramaic, a modern Aramaic language, kat (or qat, depending on the dialect) is used as a complementizer and is related to the relativizer. Though it is less common in casual speech, and more so in formal conversation.


In Hebrew (both Modern and Ancient) two complementizers coexist:[1] שֶ [ʃe], which is either related to the relativizer ‘asher ( < Akkadian ‘ashru ‘place’) and/or to the pronominal Proto-Semitic dhu ('this'); and כִּי [ki], which is also used as a conjunction meaning 'because, when'. In modern usage, the latter is reserved for more formal writing.

American Sign LanguageEdit

While some manual complementizers exist in American Sign Language they are usually expressed non-manually by grammaticalized facial expressions. Conditional clauses, for example, are indicated by raised eye-brows. If a manual complementizer is used it is also accompanied by a facial expression.[2] The non-manual marking of complementizers is a common phenomenon found in many sign languages and it was even suggested that C-categories are universally marked with the face in sign languages.[3]

See alsoEdit


  1. ^ Pages 79–81 of Zuckermann, Ghil'ad (2006), "Complement Clause Types in Israeli", Complementation: A Cross-Linguistic Typology, edited by R. M. W. Dixon and Alexandra Y. Aikhenvald, Oxford: Oxford University Press, pp. 72–92 (Chapter 3).
  2. ^ Liddell, Scott K. (1980): American sign language syntax. The Hague: De Gruyter.
  3. ^ Bross, Fabian (2020): The clausal syntax of German Sign Language. A cartographic approach. Berlin: Language Science Press.


  • Rosenbaum, Peter S. (1967). The grammar of English predicate complement constructions (PDF). Cambridge, MA: MIT Press.
  • Legate, Julie Anne. (2010). On how how is used instead of that. Natural Language and Linguistic Theory 28:121-134.