A complementizer, as used in linguistics (especially generative grammar), is a syntactic category (part of speech), roughly equivalent to the term subordinating conjunction in traditional linguistics. For example, the word that is generally called a complementizer in English sentences like Mary believes that it is raining. Linguistics is the scientific study of human language, and someone who engages in this study is called a linguist or linguistician. ... It has been suggested that this article or section be merged with Generative linguistics. ... In grammar, a lexical category (also word class, lexical class, or in traditional grammar part of speech) is a linguistic category of words (or more precisely lexical items) that are usually defined by their particular syntactic or morphological behaviours. ... In grammar, a conjunction is a part of speech that connects two words, phrases, or clauses together. ...

The standard abbreviation for complementizer is C. The complementizer is widely held to be the syntactic head of a subordinate 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 the fact that it is commonly the last element in a clause in languages like Korean or Japanese in which other heads follow their complements, and always first in "head-first" languages such as English. In linguistics, the head is the main part of a compound or phrase. ... A clause is a group of words consisting of a subject and a predicate, although, in non-finite clauses, the subject is often not explicitly given. ... The word complement (with an e in the second syllable, not to be confused with a different word, compliment with an i) has a number of uses. ...

It is common for the complementizers of a language to be borrowed from other syntactic categories (a process known as grammaticalization). Across the languages of the world, it is especially common for determiners to be used as complementizers (e.g. English that). Another frequent source of complementizer vocabulary 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 borrowed as a complementizer. (The sequence for there in this sentence is clearly not a prepositional phrase.) In many languages of West Africa, the form of the complementizer can be related to the verb say. Grammaticalisation, also referred to as Grammaticalization, Grammatisation or Grammatization is a theory describing the change of a content word (lexical morpheme) into a function word or grammatical affix. ... Determiners are words which quantify or identify nouns. ... An interrogative word (also known simply as an interrogative) is a function word used for the item questioned in a question. ... A prepositional phrase is a linguistic term for a phrase whose head is a preposition. ...