Unlike movie stars Steven Seagal and Morris the Cat (okay, so he's dead), interjections show strong emotion. Because interjections are not linked grammatically to other words in the sentence, they are set off from the rest of the sentence with a comma or an exclamation mark.
Interjections show strong emotion. Often, interjections will be set off with an exclamation mark. Although any word that shows strong feelings can be an interjection, look for the usual suspects: Wow!, Zap!, Pop!, and the rest of the family.
With interjections, a little goes a long way. Use these marks of punctuation as you would hot pepper or hysterics, because they are strong and edgy.
Excerpted from The Complete Idiot's Guide to Grammar and Style © 2003 by Laurie E. Rozakis, Ph.D.. All rights reserved including the right of reproduction in whole or in part in any form. Used by arrangement with Alpha Books, a member of Penguin Group (USA) Inc.