Summary

The standard observation is that complementizers corresponding to English that involve the illocutionary force of the clause, but the situation is not that simple, as factivity and modality may come into play, too. Complementizers are cross-linguistically systematically morpho-phonologically identical to other categories like nouns, verbs, and adpositions (that is, prepositions and post-positions). Recently there have been attempts to account for the formal identity of complementizers with other categories by decomposing the complementizer morpheme into smaller pieces. New ways of thinking about function words like complementizers and (some) prepositions involve digging into their internal structure(s) through determining the presence or absence of structural homogeneity within and across languages or by taking a nanosyntactic approach to cross-category syncretism.