When the entire subject or predicate attribute consists of more than one word, there is generally some one word that can be chosen as the base, or the main part of the expression.

In Sentence 4, Exercise 7, the entire subject is the words, the leaves of the plant, but the word leaves is the base of the expression; that is, it can serve alone as the subject.

In Sentence 5, the words very old are the complete predicate attribute; but the one word old is the base of the expression. It can serve alone as the predicate attribute. The words, Man is old, make a sentence.

In Sentence 6, it is the act of building a snow fort that is asserted, but we may take the one word built to express the act.

In Sentence 7, there is no one word that can serve as predicate attribute. The words of great age are all needed to express condition.

When the terms subject and predicate attribute are used in the following pages, they generally refer to the base of the expression.