The project investigates complex sentences with embedded clauses, focusing on object clauses after verbs like say, believe, or hope, and comparing them with relative and adverbial clauses. While all share certain traits—such as complementizers, whose forms vary across languages and dialects—adverbial clauses use semantically transparent markers (e.g., while, although), and relative clauses modify a “host” in the main clause. Complement clauses, by contrast, lack an obvious host, prompting debate between their interpretation as arguments or as expressing a mental or speech act with propositional content. The project hypothesizes a uniform “tripartite” embedding structure: a (possibly silent) anchor in the matrix clause, the embedded clause’s propositional content, and a complementizer linking them. Research centers on Germanic, Greek, and Romance, with comparisons to Basque and Hungarian.