We use oh as an interjection to express surprise or disappointment: We’re almost out of petrol. Oh! We’d better find a station. Amanda is very good on the violin. She used to play in an orchestra. Oh! I never knew that. It’s going to cost quite a lot of money to fix the car. Oh.

Adding the extra expression with the word “oh” just elevates the whole statement and delivers more emotion. What Part of Speech Is Oh? In English, “oh” is classified as an interjection, which basically means it’s a word used to express strong emotions or feelings.

Oh is an interjection - Word Type Expression of surprise. "Oh! I didn't see you there." Expression of wonder, amazement, or awe. "Oh, wow! That's amazing." Expression of understanding, recognition, or realization. "Oh, so that's how it works." A word to precede an offhand or annoyed remark.