Interjections are words or phrases used to exclaim,protest or command. They sometimes stand by themselves, but they are often contained within larger structures.
Examples of interjections: Wow! ,Oh!,Damn!,Ouch!
A sub class of interjection is the onomatopoeia-an interjection resembling sounds emmited by certain objects or animals Examples:Moo! Meow! Woof! Tick-Tock! Plop! Beep!