A word spoken all of a sudden such that it expresses various states of our mind (happiness, sorrow, surprise, etc.) is called an Interjection.
Examples:
- Hello! May I know your name?
- Bravo! An extraordinary achievement.
- Hurrah! We have defeated the opponent.
- Hush! Someone’s at the door.
- Wow! A great piece of beauty.
We see that all the highlighted words in the above sentences (Hello, Bravo, Hurrah, Hush, and Wow) are the suddenly-uttered words that express different states of our mind (salutation, appreciation, joy, instruction to be quiet, and pleasure or surprise, respectively). Thus, they are all interjections.
Interjections are followed by an exclamation mark (!). Some sentences, wherein interjections are used, take an exclamation mark at the end of the sentence. Besides the normally used interjections, some other words can also be converted into interjections with the aid of an exclamation mark.
Some unconventional interjections are shh, ho-ho, oho, boo, lo, ugh, hump, ahem, ow, whoops, hi, ho, yuk, help, tut-tut, pooh, etc. However, these interjections are not commonly used.
The sentences carrying interjections are called exclamatory or interjectory sentences and end with a mark of exclamation (!).