The document discusses different types of clauses that can be used in sentences, including full clauses, reduced clauses, and non-factual clauses. Full clauses have a subject pronoun and can be modified fully by verbs. Reduced clauses lack these characteristics. Non-factual clauses use modal verbs like "should" and can be ambiguous depending on whether they end in "s". The document also covers gerund clauses, verbal nouns, and syntactic ambiguity that can arise from coordination and modifiers.