Interjections are words or phrases used to exclaim, protest or command. They sometimes stand by themselves, but they are often contained within larger structures.
Most mild interjections (such as yes, no, well, right, okay, eh, indeed, oh) are set off from the rest of the sentence with a comma or set of commas. For example:
- Oh, I don’t know about that.
- Nice weather, eh?
- Well, what did I say?
More forceful interjections (such as ouch, yeah, yuck, wow, oops), however, are followed with an exclamation mark. For example:
- Oops! I shouldn’t have said that.
- Yuck! This milk is off!
- Wow! I won the lottery!
Interjections are rarely used in formal or academic writing.
You can find a list of interjections, with examples of their usage and punctuation, at the Dictionary of Interjections.