Interjections are words or expressions which are inserted into a sentence to convey surprise, strong emotion, or to gain attention. Interjections are usually placed at the beginning of a sentence. They have no grammatical connection to the sentence in which they occur; therefore, interjections may stand alone. In addition, if an interjection is mild, it is followed by a comma. If it is strong, it is followed by an exclamation point. In no instance should an interjection with a comma or exclamation point be followed by a period or comma respectively.

Examples include words like: Oh, Darn, Hey, and Well.

The following are two examples of the proper usage of interjections in sentences:

Well, I suppose I should stay home and study this weekend.
Darn! I broke my fingernail.