=> O

interjection
[Date: 1500-1600; Origin: O 1]
used when you want to get someone's attention or continue what you are saying
　Oh, look, I think that's Harry over there.
　Milk, cereal, juice - oh, and put lettuce on the list too.
used when you are giving an answer to a question
　'Have you met his wife?' ' Oh, yes, I know her quite well.'
　'I hope Jenny won't be angry.' ' Oh, no, don't worry about that.'
oh, okay/all right
　'Can you lend me ten pounds?' 'Oh, all right, but only until tomorrow.'
used to make a slight pause when you are speaking
　I met your friend in town, oh, what's her name?
used to show that you are very happy, angry, disappointed etc about something
　Oh, aren't those flowers gorgeous!
　Oh, how awful!
　Oh, no! I've left my keys in the car!
oh, good/great
　Oh, good, you're still here.
oh, God/oh, dear etc
　Oh, God, I forgot all about it!
　Oh, well, never mind.
used to show that you are surprised about something
　'Frances has left her husband, you know.' 'Oh, has she?'
　Oh, I didn't know that.