Definition: A noun (or noun substitute such as a pronoun, phrase or gerund) that receives action of or is affected by the action of a verb within a sentence; or a noun or noun substitute that is preceded by a preposition that indicates the relationship of that noun with another word in the sentence.
An object that receives the action of a verb is known as a direct object. An object that is affected by a verb that acts on a direct object is an indirect object. (In English, a verb that has an indirect object must also have a direct object. In Spanish, an indirect object can exist in a sentence that doesn't have a direct object.)
An object that follows a preposition is known as a prepositional object. In English, but not Spanish, it is possible for a prepositional object to be separated from the preposition (as in "Where are you going to?," where "to" is the preposition and "where" is the prepositional object), although this practice is frowned upon by some purists.
Also Known As: In English, some but not all objects are also known as complements. In Spanish, both objeto and complemento are used to refer to the three types of objects.
Examples: In the sentence "I gave him the book belonging to my mother," "him" is an indirect object, "book" is a direct object, and "mother" is a prepositional object. In the equivalent Spanish sentence, "le di el libro de mi madre, le is an indirect object, el libro is a direct object, and mi madre is a prepositional object.