Complements are one of the five types of clause element. The others are: subjects, verb phrases, objects, and adverbials.

• The complement of a clause is the element that immediately follows the verb element in clauses with the subject + verb + complement (subject) pattern (S + V + Cs) or with the subject + verb + object + complement (object) pattern (S + V + O + Co). Here are two examples of each type (the complements are marked) :

(S + V + Cs)

Sara is an unhappy woman.
Sara is unhappy.

(S + V + O + Co)

Sara called Harry a liar.
Sara considers Harry dishonest.

• Notice that in the first member of each of the above pairs, the complement is a noun phrase and in the second an adjective phrase. In all four cases — as in all instances of these two patterns — there is a “copular” relation between the complement and another element of the clause. In the two examples of the (S + V + Cs) pattern, the relation is between the complement and the subject. In the two examples of the (S + V + O + Co) pattern, the relation is between the complement and the object. In clauses with the (S + V + Cs) the copular relation is indicated by a copular verb which links the subject and the object. In clauses with the (S + V + O + Co) pattern there is no copular verb between the subject element and the complement object element but there is an implicit copular link as is indicated by the possibility of “rephrasings” such as “Sara said ,‘Harry is a liar.’”

• The normal semantic role of both types of complement is to refer to an “attribute” (i.e. a quality) of the referent of the subject or object. For example, in, “Sara is Harry’s” wife, the subject complement, “Harry’s wife,” refers to an attribute of the same person, Sara, who is referred to by the subject. Similarly, in “Sara and Harry made their guests comfortable,” the object complement, “comfortable” refers to an attribute of the same people, the guests, who are referred to by the object.

• It is important to distinguish between the meaning of the two terms, “complementation” and “complement.” The former refers to a quite general grammatical phenomenon: the complementation of a word is a phrase or clause which “completes” (or “specifies”) the meaning of that word. For example, in “Harry believes that Sara is faithful,” the clause “that Sara is faithful” is the “complementation” of the verb “believe.” And in “Harry is afraid of Sara finding out about his affair with Jill,” the prepositional phrase that follows the adjective “afraid” is its complementation. “Complements” by contrast are a specific type of clause element which can occur only in a particular and well defined syntactical context. (In a sentence like “Harry is a businessman,” the complement (“businessman”) could be said to be also the complementation of be verb “be.” In “Harry believes that Sara is faithful,” however, the complementation of “believe” is not a complement but an object (i.e. another type of clause element.) (See also Note 2 on the reference page.)