A subject complement is a word or phrase that follows a linking verb and describes or renames the subject of the sentence. Subject complements are essential to understanding sentence structure because they complete the meaning of linking verbs—verbs that don't express action but rather connect the subject to additional information. In this thorough guide, you'll learn the two types of subject complements, how linking verbs work, and how to identify and use complements correctly in your own writing.
Table of Contents
- What Is a Subject Complement?
- Understanding Linking Verbs
- Predicate Nouns (Predicate Nominatives)
- Predicate Adjectives
- Subject Complements vs. Direct Objects
- How to Identify Subject Complements
- Compound Subject Complements
- Phrases as Subject Complements
- Clauses as Subject Complements
- Common Errors with Subject Complements
- Practice Exercises
What Is a Subject Complement?
A subject complement is a noun, pronoun, adjective, or phrase that appears after a linking verb and provides essential information about the subject. Without a subject complement, a sentence with a linking verb would be incomplete. Consider the difference:
Incomplete: "The cake is." (Is what?)
Complete: "The cake is delicious." (Subject complement: "delicious")
Complete: "The cake is a masterpiece." (Subject complement: "a masterpiece")
Subject complements serve one of two functions: they either rename the subject (predicate nouns) or describe the subject (predicate adjectives).
Understanding Linking Verbs
Subject complements only appear after linking verbs. A linking verb connects the subject to the complement without expressing action. The most common linking verb is "be" in all its forms (am, is, are, was, were, been, being), but many other verbs can function as linking verbs.
Common Linking Verbs
| Category | Verbs |
|---|---|
| Forms of "be" | am, is, are, was, were, be, been, being |
| Sensory verbs | look, sound, smell, taste, feel |
| State-of-being verbs | appear, seem, become, grow, remain, stay, turn, prove |
How to Test for a Linking Verb: Replace the verb with a form of "be" (am, is, are). If the sentence still makes sense, the verb is functioning as a linking verb. "The soup tastes salty" → "The soup is salty" ✓ (linking verb). "She tasted the soup" → "She is the soup" ✗ (action verb).
Action Verbs vs. Linking Verbs
Many verbs can function as either action verbs or linking verbs depending on context. When they function as action verbs, they take direct objects, not subject complements:
Linking: "The flowers smell wonderful." (Subject complement: "wonderful" describes "flowers")
Action: "She smelled the flowers." (Direct object: "the flowers" receives the action)
Predicate Nouns (Predicate Nominatives)
A predicate noun (also called a predicate nominative) is a noun or pronoun that follows a linking verb and renames or identifies the subject. The predicate noun and the subject refer to the same person, place, thing, or idea.
"My mother is a teacher." (Mother = teacher)
"Abraham Lincoln was the 16th president." (Lincoln = president)
"The winner is she." (Winner = she)
"That building has become a landmark." (Building = landmark)
Notice how in each sentence, you can reverse the subject and the predicate noun, and the sentence still makes logical sense: "A teacher is my mother." "The 16th president was Abraham Lincoln." This reversibility is a key characteristic of predicate nouns.
Predicate Nouns vs. Direct Objects
A critical distinction: predicate nouns rename the subject, while direct objects receive the action of a verb. They are never the same as the subject:
Predicate noun: "She is a doctor." (She = doctor; linking verb)
Direct object: "She visited a doctor." (She ≠ doctor; action verb)
Predicate Adjectives
A predicate adjective is an adjective that follows a linking verb and describes the subject. Unlike attributive adjectives (which come before a noun), predicate adjectives come after the verb.
"The sky looks blue." (Describes "sky")
"The children seem happy." (Describes "children")
"The test was difficult." (Describes "test")
"The milk smells sour." (Describes "milk")
Predicate Adjectives vs. Adverbs
A common error is using an adverb instead of a predicate adjective after a linking verb:
✗ "The soup tastes badly." (This means the soup is bad at tasting things.)
✓ "The soup tastes bad." (This means the soup has a bad taste.)
✗ "I feel badly about the mistake." (Suggests impaired sense of touch.)
✓ "I feel bad about the mistake." (Describes your emotional state.)
After linking verbs, use adjectives (not adverbs) because you are describing the subject, not the verb.
Subject Complements vs. Direct Objects
| Feature | Subject Complement | Direct Object |
|---|---|---|
| Follows | A linking verb | An action verb |
| Function | Renames or describes the subject | Receives the action of the verb |
| Same as subject? | Yes (renames) or describes | No (different entity) |
| Example | "She is a nurse." (She = nurse) | "She helped a nurse." (She ≠ nurse) |
How to Identify Subject Complements
- Find the verb. Is it a linking verb or an action verb? (Use the substitution test with "be.")
- Look after the verb. Is there a noun/pronoun that renames the subject? → Predicate noun. Is there an adjective that describes the subject? → Predicate adjective.
- Test the relationship. Does the word after the verb equal or describe the subject? If yes, it's a subject complement.
Compound Subject Complements
A sentence can have more than one subject complement, forming a compound complement:
"The stew smells spicy and delicious." (Two predicate adjectives)
"He is both a writer and a painter." (Two predicate nouns)
"The weather will remain cold, windy, and gray." (Three predicate adjectives)
Phrases as Subject Complements
Subject complements can be more than single words. Various types of phrases can serve as subject complements:
Noun Phrases
"Her greatest achievement was graduating with honors from medical school."
Prepositional Phrases
"The children are in the garden."
"The package is on the counter."
Infinitive Phrases
"Her dream is to travel the world."
"The goal was to finish by Friday."
Gerund Phrases
"His favorite hobby is collecting rare coins."
Clauses as Subject Complements
Entire clauses can function as subject complements. These are typically noun clauses introduced by words like "that," "what," "whoever," "whatever," etc.:
"The problem is that we don't have enough time."
"The question remains whether they will accept our offer."
"Home is wherever you feel safe."
Common Errors with Subject Complements
1. Using Adverbs Instead of Adjectives
✗ "She looks beautifully."
✓ "She looks beautiful."
2. Pronoun Case Errors
In formal English, use subject-case pronouns (I, he, she, we, they) after linking verbs, because the pronoun renames the subject:
✓ "The winner was she." (formal)
✓ "It is I." (formal)
In informal speech, objective case ("It's me," "That's him") is widely accepted and considered standard in casual contexts.
3. Confusing Action and Linking Uses
"He grew tired." (Linking: "tired" describes "he")
"He grew tomatoes." (Action: "tomatoes" is a direct object)
Practice Exercises
Identify the subject complement in each sentence and classify it as a predicate noun or predicate adjective:
- "The cake tastes wonderful."
- "My sister is an engineer."
- "The situation became unbearable."
- "That man is the principal."
- "The flowers smell fragrant."
- "Her ambition was to become a pilot."
Answers: 1. "wonderful" — predicate adjective. 2. "an engineer" — predicate noun. 3. "unbearable" — predicate adjective. 4. "the principal" — predicate noun. 5. "fragrant" — predicate adjective. 6. "to become a pilot" — predicate noun (infinitive phrase renaming "ambition").
Key Takeaway: Subject complements complete the meaning of linking verbs by renaming or describing the subject. Predicate nouns rename the subject; predicate adjectives describe it. Always use adjectives—not adverbs—after linking verbs, and remember that the subject and its complement refer to the same entity.