The word “interjection” literally means “thrown in between.” Interjections express emotion and are capable of standing alone. Common interjections are Ugh! or Wow! Oh! Hey! Ow!
Interjections are often followed by an exclamation mark (!). Or, they can be followed by a comma (,). It depends on the importance of the emotion.
- Hey! That barn is on fire.
- Hey, I broke a nail.
Even when interjections are a part of a sentence, they don’t directly relate to the grammar of that sentence.