Target audience: intermediate learners.

Complementizers are a [[ grammatical category]] which is used to allow a clause to serve a [[grammatical function ]] (e.g. subject, object) within a larger sentence. English examples include the words that,1 if, and whether.

In traditional grammar, complementizers are part of the larger category of [[ conjunction ]]. Specifically, they are traditionally considered subordinating conjunctions (as opposed to coordinating conjunctions such as and or or).

Complementizers and word order

Conjunctions can appear either on the left or the right side of the clause. As with much crosslinguistic variation in word order, there are correlations with basic word order: object-verb languages tend to have complementizers appear on the right side of the clause (often attaching as suffixes to the verb).

[김치는 맵지만] 맛있어요
[kimchi-neun mep-jiman] masiss-eoyo
[kimchi-TOP spicy-although] tasty-POLITE
‘Although kimchi is spicy, it is tasty.’ (Korean)

Verb-object languages, by contrast, tend to have conjunctions appear on the left side.

Je sais [que tu es là.]
I know [that you are there]
‘I know that you are there.’ (French)

  1. The English word that is not always a complementizer. Consider the difference in function between the complementizer that in I know that you are here. the demonstrative pronoun that in I know that., and the demonstrative adjective I know that man.. These usages are related historically. 

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