When do you use interjection?

Answer 1

Use them when you want to show excitement or emotion.

Yes! We won the game!

You can punctuate them with an exclamation mark or with a comma if the feeling is not as strong.

Wow, this food is great.

Here is a list of interjections:

http://www.english-grammar-revolution.com/list-of-interjections.html

And here is a page that describes what they are:

http://www.english-grammar-revolution.com/what-is-an-interjection.html

Answer 2

Interjections are used to express emotions or reactions in a conversation or writing. They can convey feelings like surprise, excitement, frustration, or agreement. Interjections are typically set apart from the main sentence with punctuation marks like commas, exclamation points, or dashes.