Students read books.
In this first sentence, the predicate contains a direct object. Books is the direct object of the verb read. The verb read is a transitive verb, or a verb that requires a receiver of the action. To diagram a direct object, draw a vertical line that stands on the base.
Teachers are happy.
The second sentence contains a predicate adjective (happy). A predicate adjective always follows a linking verb.
A linking verb can also precede a predicate nominative, as in the following sentence:
My teacher is Ms. Thompson.
Notice that Ms. Thompson re-names the subject teacher.
To diagram a predicate adjective or nominative, draw a diagonal line that rests on the base.