What are Direct Objects in English?
Complements, direct objects, and transitive verbs
A complement is a word or group of words that completes the thought about the subject of a sentence.
A direct object is one kind of complement. Sometimes a sentence cannot be completed with just a subject and verb. Often, the reader needs to know the person, animal, or thing on which the verb acts. The word that receives the action of the verb is called the direct object of the verb.
If a verb requires a direct object in order to make a complete thought, we say the verb is transitive. A transitive verb makes a transition from the subject to the direct object.
By definition, a transitive verb must be an action verb because the direct object receives the action of this verb.
Examples
1. Anne Anastasi developed.
This group of words contains a subject and verb, but it does not make a complete thought. The reader asks what Anne Anastasi developed. We must add a direct object to the sentence to answer this question.
2. Anne Anastasi developed psychological tests.
Now the reader knows what Anne Anastasi developed. The word "tests" names the direct object of the verb; the word that receives the action of that verb. "Psychological" is an adjective, which modifies "tests."
What's in a direct object?
A direct object must contain a noun or word used as a noun because you must name the person, thing, or idea which receives the action of the verb. That noun can be modified with adjectives.
Examples
1. Virginia Apgar tested infant health.
Who tested infant health? Virginia Apgar (subject)
What did she do? tested (verb)
What did she test? health (direct object, "infant" indicates whose health)
2. She invented the Apgar Score.
Subject: She
Verb: invented
Direct object: Apgar Score