Interjections are words or phrases used to express an emotion or sentiment on the part of the speaker. It is also used to exclaim or protest or command. They sometimes stand by themselves, but they are often contained within larger structures.
Most mild interjections are treated as parenthetical elements and set off from the rest of the sentence with a comma or set of commas. If the interjection is more forceful, however, it is followed with an exclamation mark. Interjections are rarely used in formal or academic writing.
Now, here’s some of the list of the commonly used interjections and the correct way of using them.