This document discusses different types of complex sentences that contain subordinate clauses. It defines complex sentences as sentences that contain other sentential structures. Subordinate clauses are introduced by complementizers like "that" or conjunctions like "if" and "because". The document outlines the different functions subordinate clauses can serve, including as subjects, objects of verbs or adjectives, complements of nouns, and complements of prepositions. It also discusses adverbial clauses and the conjunctions that introduce them.