A complement is a word, phrase, or clause that completes the meaning of the verb in the predicate, and thus the sentence. The complements can be broken into the following:

 

Those following action verb: direct object, indirect object, and object complement
Those following linking verb: subject complements (predicate nominative/predicate noun, and predicate adjective)
An object complement completes an object, and a subject complement completes a subject.

 

Direct object

A direct object is a noun or pronoun that comes after a verb to complete the meaning of the verb, which is a transitive verb. The direct object receives the action of the transitive verb.
 
The following examples show the direct object in bold.
The dog followed Don.
Mary ate the chicken pie.
Someone stole the donation box and the call bell.

 

Indirect object

An indirect object is either a noun (person, thing or animal) or a pronoun that appears in a sentence after the verb and before the direct object. It can only be found in a sentence that has a direct object. The indirect object shows to whom or for whom something is done, and who receives the direct object.
 
The following examples show the indirect objects in bold.
I showed her my strawberry ice cream.
I showed my strawberry ice cream to her.
I bought my aunt a vanilla ice cream.
I bought a vanilla ice cream for my aunt.
The father drew his son a picture of a dinosaur’s face.
The company mailed the members the new brochures.

 

Object complement

An object complement can be a noun, a pronoun or an adjective. It comes immediately after a direct object, and adds to the direct object by renaming or describing it. Certain verbs are used when there is an object complement. The verbs include call, create, elect, make, and name.
 
The following examples show the object complements in bold.
His villagers hailed them heroes after their rescue mission. (them = heroes)
They called the priest a small-time crook. (priest = a small-time crook)
(The object complements are a noun and a noun phrase.)
His stare made her angry.
He painted the doghouse colourful as a rainbow
(The object complements are an adjective and an adjective phrase.)
The sales assistant caught him shoplifting.
I heard his three dogs barking.
The driver watched the ducks waddling across the road.
(The object complements are participles and a participial phrase.)
 
 

Subject complements

A subject complement is a predicate noun or a noun phrase, or a predicate adjective or an adjective phrase, or a pronoun. It follows a linking verb, a state verb, or a verb of the senses. The noun, adjective, or pronoun which is the subject complement describes, renames, or identifies the subject of a sentence. Some examples of linking verbs are am, is, are, was, were, has been, are being, become, look, and seem.

 

A predicate noun is a word or a group of words that renames the subject.

The country’s new head of state is Mr. Superb Super.
He said his mother-in-law was a silly old witch.
(The linking verbs are is and was.)

 

A predicate adjective is an adjective that describes the subject.

That fly settling on your pizza looks big.
His story about witnessing two UFOs colliding was simply unbelievable to me.
(The linking verbs are looks and was.)

 

A subject complement can be a pronoun that identifies the subject.

I still remember the hearse driver is he.
It was they, those boys there, who laughed at me when I fell down.
(The pronoun that follows a linking verb must be in the subjective case.)