Mr. President, I move that a committee be now appointed.
Fellow Workers, I rise to address you.
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:
_Comrades_, rouse yourselves.
_Men_, strike for freedom.
2. +Exclamatory expressions.+ These are nouns used in the manner in
which we have already discussed, as in the sentence:
_Nonsense!_ I do not believe a word of it.
Alas! poor _Yorick_! I knew him well.