A word or group of words that has no grammatical connection with the sentence in which it stands is called an independent element.
Independent elements are of four kinds.
2. Vocatives (or nominatives by direct address)
3. Exclamatory nominatives
4. Parenthetical expressions
a. Ah! why did I undertake this task?
b. Help arrived, alas! too late.
c. You are a strange man, Arthur.
d. Mary, come here!
e. Poor Charles! I am sorry for him.
f. Clothes! clothes! you are always wanting clothes.
g. Lucky she! we are all envious of her prospects.
The first two sentences contain interjections.
The second two sentences contain vocatives (or nominatives by direct address).
The last three sentences contain exclamatory nominatives.
When the independent word has a modifier (as in the fifth and seventh examples), the whole phrase may be treated as an independent element.
A word or group of words attached to or inserted in a sentence as a mere comment, without belonging either to the subject or the predicate, is said to be parenthetical.
1. The market, indeed, was already closed.
2. Peter, to be sure, was not very trustworthy.
3. The house, at all events, is safe.
4. The road is, I admit, very hilly.
5. Luttrell’s method, it must be confessed, was a little disappointing.
6. Richard was not a bad fellow, after all.
In analysis, an independent element is mentioned by itself and not as a part of the complete subject or the complete predicate.