What are Objects in a Sentence? The object of a sentence is the person or thing that the action in the sentence is happening to or is affected by. For example, in the sentence Sarah is reading the book, the book is the object because the book is what Sarah is reading. The object of a sentence can be a noun or a pronoun, but this lesson will only teach nouns. The next lesson will be about object pronouns. As students get older, they will learn about direct and indirect objects, but that is not co