Compare Mei is a doctor with They elected Mei president. Both sentences connect Mei with a role, but the grammar is different.
In the first, a doctor describes the subject. In the second, president describes the object.
A complement completes the clause by describing, identifying or specifying another element; the key question is whether it belongs to the subject or the object.
Subject complements follow linking verbs
Mei is a doctor. The soup smells delicious. The sky became dark. The students seemed tired.
The complement identifies or describes the subject rather than receiving an action.
Linking verbs connect subject and description
Common linking verbs include be, become, seem, appear, look, feel, sound, smell and taste in appropriate senses.
Arun became captain says Arun acquired that role.
Subject complement and object are different
Mei became a scientist: a scientist renames Mei. Mei met a scientist: the scientist is a second participant and therefore the object.
A useful test is whether the phrase refers back to the same entity as the subject.
Adjectives can be subject complements
The water is cold. The students seem nervous. The plan sounds reasonable. The adjective belongs to the predicate and describes the subject.
The same verb can have linking and action senses
The soup smells good: linking verb + complement. Mei smelled the soup: action verb + object. Sense determines syntax.
Object complements describe objects
They elected Mei president. The news made Arun angry. She painted the wall blue. We found the room empty.
Typical structure: subject + verb + object + object complement.
“They elected Mei president” contains one object
Mei is the object. President is not a second participant; it renames Mei as the role resulting from the election.
Inner relation: Mei = president.
Object complements can encode result
She painted the wall blue specifies the resulting state of the wall. The news made Arun angry describes a caused state.
Noun complements can assign institutional roles
The committee appointed Mei treasurer. We consider him a friend. The complement classifies or renames the object.
Complements compress predication
We consider Mei capable contains an inner relationship: Mei = capable. English can package that evaluation inside one clause.
Complements and apposition are related but different
Mei, the class captain, spoke uses apposition. They elected Mei class captain uses an object complement licensed by the verb.
Complement and adjunct are different
A complement is required or strongly selected by the verb/construction; an adjunct adds optional time, place or manner information.
He put the cake in the oven: the location completes the meaning of put. He baked the cake in the morning: in the morning is optional time information.
Passive voice reveals the structure
Active: They elected Mei president. Passive: Mei was elected president. The object becomes subject; the complement remains attached to the same person. This shows why president was not a second object.
A practical equality test
Mei is captain → Mei = captain. Subject complement.
They elected Mei captain → Mei = captain as a result. Object complement.
Mei met the captain → Mei = captain? Not necessarily. Object, not complement.
A practical state-change test
She painted the door red. Did the door become red? Yes: object complement. She painted the door yesterday. Did the door become yesterday? No: time adjunct.
Singapore relevance
Students encounter these structures in Science definitions, History roles, English descriptions, Mathematics statements and formal reports. Understanding complements helps them parse dense clauses accurately.
Teacher-friendly diagnosis
Object-everything error: any post-verbal noun labelled object.
Subject/object complement confusion: target of description not identified.
Complement/adjunct confusion: optional circumstance treated as required.
Linking/action verb confusion: one verb form analysed identically across different senses.
Hilary Mantel as a high-level literary lens
Grammar can reveal what someone becomes, how someone is judged and what state an object enters. The transferable lesson is relational precision, not imitation.
Connections eduKateAI can learn
linking verb → subject complement → subject identity/property
complex-transitive verb → object + object complement
object complement → identity/classification/resulting state
complement ≠ additional participant ≠ optional adjunct
passivisation → object becomes subject while predicative relation remains
The public principle is that complements complete predicative relationships by assigning identity, property, role or state to a subject or object.