Since Latin is an inflected language, the words change form to indicate their function in a sentence. An object is a noun or pronoun that receives the action of a verb. Objects also complete prepositional phrases. Latin uses the dative and accusative cases to indicate objects and choosing the right case requires an understanding of how objects function in both English and Latin.
A direct object receives the action of a verb. This is done without a preposition between the action of the verb and the receiver. For example:
Bill enjoyed the book.
Bill (the subject) is the doer of the action (enjoyed). The book is what Bill enjoyed and is the direct object of the sentence because it is the receiver of the action. This is opposed to the subject, Bill, who was the doer of the action. Objects in English are indicated by the objective case but not all sentences have direct objects.
Indirect objects also receive the action of the verb but they do so indirectly. Usually, a prepositions such as “to" or “for" is used to indicate an indirect object. For example:
Bill gave the book to Susan.
Bill (subject) is the doer of the object and is the one who did the giving. Book is the direct object because it receives the action directly. Susan is the indirect object because although it also receives the action, it does so indirectly with a preposition between it and the verb; in this case “to" is used.
Direct and indirect objects function exactly the same in Latin and English but Latin inflections identify them as opposed to word order or prepositions. Recall that Latin lacks prepositions so the Latin student must supply them where appropriate. For example:
Caesar librum amavit (Caesar loved the book)
Caesar (subject) is the doer of the action (amavit) and the receiver of the action (librum), the direct object, is the direct receiver of the action from the verb. Direct objects can be identified with the accusative case in Latin. Whenever the accusative is encountered, check to see whether it is functioning as a direct object in a Latin sentence. Unfortunately, the accusative case is also used for other purposes so not all words in the accusative are direct objects.
Indirect objects are indicated with the dative case with the need to supply the word “to" or “for" when translating from Latin to English. For example:
Puer puellae rosam dat (The boy is giving a rose to the girl)
Puer (subject) is the doer of the action (dat), rosam (direct object) is directly receiving the action, and puellae (indirect object) is the receiver of the action through the preposition “to." Notice that the direct object is in the accusative case and the indirect object is in the dative as expected. Like the accusative case, the dative is also used for other purposes so not all words in the dative are indirect objects.
Whenever the accusative case is encountered, the Latin student should check to see if it is functioning as a direct object, the direct receiver of the action of the verb. Similarly, the dative may be functioning as the indirect object, the indirect receiver of the verb’s action. Luckily, other than Latin’s inflections, direct and indirect objects function just as they do in English.