This paper is concerned with the syntactic problems raised by the grammatical phenomenon in Japanese that is called here the "complementizer." In the types of sentences under consideration here, S2 is a nominal clause. Such a clause acts as a noun phrase adjunct to the verb in S1. The noun clauses in question are often followed by a postposition which shows their grammatical relation to the main verb. The remainder of the noun phrase is the "complementizer." The complementizer may include a head noun which the clause complements. Or it may include a formal noun which is grammatically a head noun but apparently without semantic contribution to the sentence. Or it may include "to" (iu). The paper stresses the importance of distinguishing between noun clauses and relative clauses when the surface structures are the same. The relationship of the complementizers "koto" and "to,""no" as a complementizer, the ga-weakening rule, copula adjustment, and Makino's critique of formal nouns are discussed. (CFM)