An interjection could also be thought of as a exclamation. They are used to emotion, reaction or excitement and have no grammatical link to anything else within the sentence they appear.

Examples:

Ahem!, aha!, gosh!, aw!, great!, hey!, hi!, hooray!, oh!, yeah!, oops!, phew!, eh!, oh!, ouch!, hi!, well!…

Interjection example sentences:

• Phew! That was a close call.
• Wow! Did you see how big that bird was?
• Oh, I forgot to tell you that I saw your father last week.
• Hooray! You passed your exam!
• Well, what did he say?
• Yeah! Shes going with us tonight!