Complement (linguistics)

In linguistics, a complement is a word, phrase, or clause that is necessary to complete the meaning of a given expression. Specifically, it's an element that provides further information about another element in the sentence, typically a verb, noun, adjective, or preposition. A complement is different from an adjunct, which is an optional element that adds extra information but is not essential to the grammatical completeness or basic meaning of the expression it modifies.

Complements are typically divided into several types, based on what kind of element they complete and their grammatical form:

• Verb Complements: These are the most commonly discussed. They provide necessary information about the verb. Verbs can take different types of complements:

  • Direct Objects: A noun phrase that receives the action of the verb. Example: "She ate the apple."
  • Indirect Objects: A noun phrase that benefits from the action of the verb. Example: "He gave her a book."
  • Subject Complements: A noun phrase or adjective that renames or describes the subject of the verb, typically following a linking verb (e.g., be, become, seem). Example: "She is a doctor." or "He seems happy."
  • Object Complements: A noun phrase or adjective that renames or describes the direct object. Example: "They elected him president." or "They painted the house blue."
  • Clausal Complements: A clause (a group of words containing a subject and a verb) that functions as a complement. Example: "I know that he is coming."

• Noun Complements: These phrases complete the meaning of a noun. They often specify or further define the noun. These are usually prepositional phrases or clauses that follow the noun. Example: "The belief that she was innocent was widespread." or "The city of London is large."

• Adjective Complements: These phrases complete the meaning of an adjective. They often specify the reason or extent of the adjective's quality. These are frequently prepositional phrases or that-clauses. Example: "I am happy that you are here." or "She is afraid of spiders."

• Preposition Complements: These are noun phrases that follow a preposition to form a prepositional phrase. The noun phrase is the complement of the preposition. Example: "They went to the store."

The distinction between complements and adjuncts is crucial for understanding sentence structure and grammatical relationships. While complements are required for a sentence to be grammatically complete and express a full thought, adjuncts are optional modifiers that can be removed without affecting the sentence's core meaning. Determining whether a phrase is a complement or an adjunct can sometimes be complex and is a key area of study in syntactic theory.