A predicate adjective is used as a subject complement within a sentence, which serves to describe or modify the subject. This type of word is usually found after a linking verb, such as "are" or "smelled," and describes the subject that precedes it. Simple examples are the word "beautiful" in the sentence "The tall woman is beautiful," or "rancid" in the sentence "The milk smelled rancid." A predicate adjective should not be confused with a predicate nominative, which serves much the same function but is a noun that renames the subject of a sentence.
Much like other adjectives, a predicate adjective is a word that describes or modifies another word, typically a noun or pronoun. In this form, however, it acts as part of the predicate in a sentence rather than as a word within a noun phrase. The predicate is the part of the sentence that provides information about the subject. For example, in the sentence "The tall woman is beautiful," the subject is "The tall woman," while the predicate is "is beautiful."
Normally, an adjective is found with the word that it modifies, often as part of the same phrase. In the previous example, the word "tall" is an adjective that is part of the noun phrase "The tall woman." A predicate adjective, however, is not in a phrase with the word that it describes, which can lead to confusion within a sentence.
The presence of a linking verb can indicate that a predicate adjective is in the sentence and help alleviate any confusion. Linking verbs include words like "is," "tastes," and "appears." They are intransitive verbs, which means they do not require a direct object within the sentence, and the predicate adjective acts as the word or phrase that they link to the subject. Many of them can be found in sentences in which they are not a linking verb, however, so they must be with an appropriate predicate to serve this function.
In the previous example, the word "beautiful" describes the subject of the sentence. The word "is" acts as a linking verb and indicates that the predicate adjective that follows modifies the subject. A similar structure is found in the sentence, "The milk smelled rancid." The word "rancid" describes the subject "The milk;" it is connected by the linking verb, "smelled."
This should not be confused with a predicate nominative, however, which is a noun or pronoun that serves a similar function. In the sentence, "The tall woman is a teacher," the subject remains "The tall woman" and "is" continues to function as a linking verb. The predicate nominative "a teacher," however, is a noun phrase. It does not describe the subject through an adjective, but restates what it is through a noun or pronoun.