A Versus An   Sadly, a lot of people were taught the wrong rule for using the articles a and an . It's the sound of the next word that determines the word choice, not the first letter. If the next word starts with a vowel sound, use an . If the next word starts with a consonant sound, use a . That means a word starting with u or o, for example, can require a or an depending on the pronunciation: a unicorn, an uncle, a onetime deal, an owner. QUICK AND DIRTY TIP To remember that words starting with certain letters can go either way, set the image in your mind of a man playing a ukulele under an umbrella--an image that uses two u -words that require different articles.   Copyright (c) 2011 by Mignon Fogarty, Inc. Excerpted from Grammar Girl's 101 Misused Words You'll Never Confuse Again by Mignon Fogarty All rights reserved by the original copyright owners. Excerpts are provided for display purposes only and may not be reproduced, reprinted or distributed without the written permission of the publisher.