An object complement is a word or phrase that follows the direct object and describes, renames, or identifies it. It completes the meaning of what happened to the object, not the action itself.
Here happy describes her (the object), not the news. Without it, The news made her is incomplete.
An object complement can be an adjective or a noun. Adjectives describe the object; nouns rename it.
The basic pattern is always the same: Subject + Verb + Object + Object Complement.
Adjective complements
The most common type. An adjective after the direct object tells you what the object became, how it ended up, or how someone perceives it.
If you remove the adjective, the sentence either changes meaning or makes no sense. She keeps her apartment sounds like she is storing it somewhere. I find this documentary sounds like you located it. The adjective is not optional -- it completes the idea.
Noun complements
A noun or noun phrase after the direct object renames it -- gives it a new title, role, or identity.
Without the noun complement, these sentences are vague: The board appointed James leaves the reader wondering what position.
Verbs that take object complements
Not every verb works with an object complement. The ones that do tend to describe creating a state, expressing a judgment, or assigning a name or role.
Make
The most common. It describes causing the object to become something.
Find and consider
Both express a personal judgment about the object.
Find often implies discovery -- you encountered something and formed an opinion. Consider implies a deliberate judgment.
Call and name
Both assign a label or title to the object.
Elect and appoint
Both assign a formal role.
Keep and leave
Both describe maintaining or abandoning the object in a particular state.
Paint and colour
Physical change of appearance.
Drive
Describes pushing someone into an emotional state.
Object complement vs. adverb
This is where most confusion happens. Both come after the object, but they modify different things.
An adverb modifies the verb -- it answers how? about the action.
An object complement modifies the object -- it answers what did the object become? or what state is the object in?
Quickly describes how she made it -- the speed of her action. It is an adverb.
Happy describes him -- his resulting state. It is an object complement.
The test is straightforward: does the descriptor refer to the object or to the verb? If it refers to the object, it is a complement. If it refers to the action, it is an adverb.
A few more pairs to see the difference clearly:
A note on "make + verb"
The verb make has another pattern that looks similar but works differently: make + object + base verb.
Here leave is not a complement describing him -- it is a verb describing what he was forced to do. This is a separate grammatical structure covered separately.
Common mistakes
Using an adverb instead of an adjective
Dropping the complement entirely
Wrong word order
Confusing subject complement and object complement
- he is happy (subject complement -- happy describes he after a linking verb)
- the news made him happy (object complement -- happy describes him after the direct object)
Missing object before the complement