it is an interjection that is used to refer to a sound or expression of surprise, disbelief, or disappointment.
it is typically not used in the middle of sentences, but at the beginning or the end.
1. 'Oh! I can't believe he said that!'
2. 'Oh, I'm so sorry to hear that.'
3. 'Oh, I think I know the answer to that.'
use 'oh' to express agreement (at the beginning of a sentence generally), and when to use it to express surprise or shock (usually at the end of a sentence). Common mistakes include placing 'oh' in the middle of sentences or using it for a reaction other than surprise or shock.