In grammar, a complement is a word or group of words that completes the meaning of a verb, noun, or adjective. It provides essential information needed to make a sentence feel complete. Complements are not optional-they fill gaps left by incomplete predicates.
Complements differ from modifiers. Modifiers add detail but aren't required for grammatical completeness. A complement is necessary. For example, "She is happy" contains the subject "she," the linking verb "is," and the complement "happy." Without "happy," the sentence lacks closure. "She is" alone is incomplete.
Complements appear in two main forms: subject complements and object complements. Subject complements follow linking verbs and describe the subject. Object complements follow transitive verbs and describe the direct object. Both serve to complete meaning, but their roles differ based on structure.
Complements are tied to specific verb types. Linking verbs such as "be," "seem," "become," "appear," and "feel" do not express action. Instead, they connect the subject to a complement that describes it. These verbs require a complement to form a complete predicate.
For example: "The soup tastes salty." Here, "tastes" is a linking verb. "Salty" is a predicate adjective-a type of subject complement. The sentence would be ungrammatical without "salty": "The soup tastes" leaves the listener waiting for the rest of the description.
Another common pattern uses a noun after a linking verb. "She became a doctor." "Became" links "she" to "a doctor," which identifies her role. This noun is called a predicate nominative. It's not describing the subject-it's renaming it.
There are four primary types of complements in English grammar. Each serves a distinct purpose and appears in a specific syntactic position.
| Type | Purpose | Example | Function |
|---|---|---|---|
| Predicate Adjective | Describes the subject | The cake smells delicious. | "Delicious" completes the meaning of "smells" |
| Predicate Nominative | Renames the subject | He is a teacher. | "A teacher" identifies "he" |
| Object Complement | Describes the direct object | They elected her president. | "President" defines "her" after the verb "elected" |
| Subject Complement | General term for both predicate adjective and nominative | She seems tired. | "Tired" completes the subject "she" via the linking verb "seems" |
Not all verbs take complements. Action verbs like "run," "write," or "jump" don't require complements. "She runs fast" is complete without adding anything. But "She feels tired" requires "tired" to finish the thought.
A non-obvious distinction: some words look like complements but aren't. Consider "I saw him leave." "Leave" is not a complement-it's an infinitive verb. "Him" is the object of "saw," and "leave" is part of a verb phrase. This is not a complement because "leave" doesn't describe "him." It's a separate clause.
Many learners mistake adverbial phrases for complements. For example, "She is at home." "At home" is a prepositional phrase indicating location. It's not a complement because "at home" doesn't describe or rename the subject. It adds context, not completion.
Another frequent error is confusing complements with objects. "She gave the book to John." "The book" is the direct object. "To John" is an indirect object. Neither is a complement. Complements come after linking verbs or with transitive verbs that assign identity or state.
Consider: "They made the project easy." "Easy" is a complement. It describes the object "project." "Made" is a causative verb that takes an object and a complement. This is different from "They made the book," where "book" is just the object. Adding "easy" completes the meaning.
Take this sentence: "The interview felt exhausting." "Felt" is a linking verb. "Exhausting" is a predicate adjective. Together, they form a complete predicate. Remove "exhausting," and the sentence becomes "The interview felt"-an incomplete thought.
Now consider: "The committee declared the proposal invalid." "Declared" is a transitive verb. "The proposal" is the direct object. "Invalid" is an object complement-it describes the object. Without "invalid," the sentence lacks closure. "Declared the proposal" is not enough.
I once observed a student write: "The movie was boring." They meant to describe the film's effect. But "boring" is correct-it's a predicate adjective. If they had written "The movie was a waste," "a waste" would be a predicate nominative. Both are valid complements, but they serve different grammatical functions.
Complements are not optional. They're required by certain verbs. The verb "seem" demands a complement. "She seems tired" is correct. "She seems" is not. The same applies to "become," "remain," "prove," and others. These verbs are incomplete without a complement.
Complements complete meaning. They are not extras. A sentence like "The test was difficult" relies on "difficult" to finish the idea. Without it, the statement is grammatically broken.
Complements are not the same as modifiers. A modifier adds detail; a complement completes meaning. "She looked angry" uses "angry" as a complement. "She looked angrily" uses "angrily" as an adverb modifying "looked." The difference changes the entire meaning.
Understanding complement definition grammar improves clarity in writing and speaking. It prevents errors like "I am happy with my job" (correct) versus "I am happy my job" (incorrect-missing complement after "happy").