A vs. An
Use the article an before a word beginning with a vowel (a,e,i,o,u) or a vowel sound (words beginning with a silent h as heir, hour). Words that start with eu or u that are pronounced with a long u or pronounced like "you" use the article a before them.
Examples: an egg, an hour, an orange, an idea, a house, a mouse, a river, a boy, a ukulele, a eucalyptus tree.
Instructions: Use the correct article before the following words.