Interjection (noun)

1. A word or phrase, such as oh, wow, or yes, that is used to express strong emotion or to emphasize a statement.
2. A sound or gesture used to indicate surprise, doubt, or a range of other feelings.

Origin:

This word comes from the latin word interiectio, which means "a throwing between", formed by inter meaning "between" and iactio meaning "a throwing".

Examples:

1. Oh! That's incredible!
2. Interjections such as "oh" or "um" are often used in conversation.
3. Wow! I can't believe it!
4. She made an interjection of surprise when she saw the cake.
5. The interjection "yes!" was shouted when the team won the game.