Besides the principal elements in a sentence, there are SUBORDINATE ELEMENTS. These are the Attribute Complement, the Object Complement, the Adjective Modifier, and the Adverbial Modifier.
Some verbs, to complete their sense, need to be followed by some other word or group of words. These words which "complement," or complete the meanings of verbs are called COMPLEMENTS.
The ATTRIBUTE COMPLEMENT completes the meaning of the verb by stating some class, condition, or attribute of the subject. Ex: My friend is a STUDENT. I am WELL, The man is a GOOD Student. Well, and good complete the meanings of their respective verbs, by stating some class, condition, or attribute of the subjects of the verbs.
The attribute complement usually follows the verb be or its forms, is, are, was, will be, etc. The attribute complement is usually a noun, pronoun, or adjective, although it may be a phrase or clause fulfilling the function of any of these parts of speech. It must not be confused with an adverb or an adverbial modifier. In the sentence, He is THERE, there is an adverb, not an attribute complement.
The verb used with an attribute complement, because such verb joins the subject to its attribute, is called the COPULA ("to couple") or COPULATIVE VERB.
Some verbs require an object to complete their meaning. This object is called the OBJECT COMPLEMENT. In the sentence, I carry a BOOK, the object, book, is required to complete the meaning of the transitive verb carry; so, also in the sentences, I hold the HORSE, and I touch a DESK, the objects horse and desk are necessary to complete the meanings of their respective verbs. These verbs that require objects to complete their meaning are called Transitive Verbs.
ADJECTIVE and ADVERBIAL MODIFIERS may consist simply of adjectives and adverbs, or of phrases and clauses used as adjectives or adverbs.