In these sentences, Mr. President and Fellow Workers are nouns used independently; that is, they are neither the subject of the sentence nor used as object or predicate complement. They are independent of all other words in the sentence.

The most common use of words used independently in direct address occurs with imperative sentences. For example:

2. Exclamatory expressions. These are nouns used in the manner in which we have already discussed, as in the sentence:

3. Words and phrases used parenthetically, as for example:

In these sentences such words as, however, and such phrases as, by the way, and, it seems, are used independently,—in parenthesis, as it were; that is, they are just thrown into the sentences in such a way that they do not modify or depend upon any other word in the sentence. When we analyze our sentences, these independent words are not considered as elements of the sentences in which they are used. It is sufficient to say that they are independent words.

4. Conjunctions used as introductory words. We have noted the use of conjunctions like the co-ordinates and, but, etc., and the subordinates because, in order that, so, for, wherefore, how, whether, etc., which are used to introduce sentences and connect them in thought with sentences and paragraphs which have gone before.