Object clauses are subordinate clauses that function as objects in English sentences. They can serve as objects of verbs, prepositions, or adjectives. For example, in the sentence "I know that he is a student", the clause "that he is a student" acts as the object of the verb "know".
Object clauses are introduced by different types of words. The conjunction "that" is the most common, often omitted in informal speech. Interrogative pronouns like who, what, which introduce clauses asking about people or things. Interrogative adverbs like when, where, why, how ask about time, place, reason, or manner. Finally, "whether" or "if" introduce clauses expressing uncertainty or choice.
Object clauses serve three main functions. First and most commonly, they act as objects of verbs, as in "I know that he is here." Second, they can be objects of prepositions, like "We talked about what happened." Third, they function as objects of adjectives, such as "I am sure that he will come." Understanding these different functions helps identify object clauses in complex sentences.
A crucial rule for object clauses is word order. Object clauses always use declarative word order, which means subject plus verb plus other components. This rule applies even when the main clause is a question. For example, we say "Do you know where he lives?" not "Do you know where does he live?" The object clause maintains its declarative structure regardless of the main clause type.
An important feature of object clauses is that the conjunction 'that' can often be omitted in informal speech and writing. For example, we can say either "I think that he is right" or simply "I think he is right." However, 'that' cannot be omitted in all situations. It must be kept after adjectives, as in "I'm sure that he will succeed," and after prepositions. In formal writing, 'that' is usually retained for clarity and precision.