In the sentence, Oh, this will never do!
the word Oh,
expresses a feeling in the sentence. It does not connect grammatically with any part of the sentence, but it bears a relationship to the sentence as a whole. It is a word thrown in
and is called the interjection. An interjection is a word that expresses sudden or
strong feeling. Examples of the interjection are: EX. Pshaw!
I am very disappointed in you. EX. Alas!
He made it home after ten years at sea.EX. "Ah!"
breathed the crowd. EX. Hurrah!
We've won the game! EX. Good work!
That's excellent bowling!EX.
Have mercy on Thy people, O
Lord! Proper punctuation with interjections
When we use an interjection as a real exclamation, we follow it with an exclamation point. If, however, we use it as a mild, or rhetorical, exclamation, then we follow it with a comma.Examples: EX.
Oh, to be sure, that is probably true.EX.
Mercy! What a scare that sound gave me! EX.
Hurrah! hurrah! We scored! EX.
Hail! holy light, shower down
upon me from Heaven. EX.
O God in heaven! Fill my life with vivid light!NOTE
We use the capital O
(without a comma) to refer to some object in awe or admiration or reverence. This is called apostrophe
is used as a vocative or mild exclamation. Since apostrophe is a poetic figure of speech, we usually see the capital O
mostly in poetry, while we see the more common Oh
both in prose and in poetry.