An interjection is used in the sentence to express our emotions and feelings. It is grammatically not related to the part of the sentence. An interjection is a part of speech. They can be in any form a word, a short phrase usually accompanied by an exclamation mark to punctuate them. We often use them in our daily conversations but might not realize it. Such as ‘hi’, ‘hey’, ‘hello’, etc.
Some interjections stand-alone or some between the sentences there is no such rule. You could use an interjection before or after a sentence that reveals what’s going on.
Interjection often has an exclamation point, but it is not necessary to use it. An interjection can be used in a sentence, but it is important to separate it from the rest of the sentence.
It is good to use Interjection to express emotions and excitement. However, one should avoid it in formal writing, as it creates a casual approach.