“A” and “an” are both indefinite articles that are used to introduce nonspecific nouns. A popular misconception is that the first letter of the word indicates whether you should use “a” or “an” as the article. However, this is not the case. Instead, the sound of the word lets you know which article to use. For words that have a consonant sound, use “a” as the article. For words that have a vowel sound, use “an” as the article. While this may seem simple in theory, this rule can get complicated in practice. For example, since this grammatical rule is based on phonetics, different articles are used for the same word in British English and American English. In British English, the word “herb” is pronounced with the “h” sound and therefore uses “a” as the article. However, in American English, the “h” is silent in “herb,” so the first syllable is pronounced with the “e” sound, using “an” as the article. The letter “h” is sometimes silent at the beginning of a word. Therefore, words that start with the letter “h” can have a vowel or consonant sound and can use either “a” or “an” as the article. When the “h” is silent, the first syllable of the word is a vowel sound, so you use “an” as the article. Some examples include honor, honest, hour, and herb. Words that start with “h” and begin with the “h” sound—habit, hotel, hero, and house, for example—use “a.” There are still some exceptions to this rule, such as the word “historic.” You can say “a historic” or “an historic” depending on your pronunciation of the word. Like the letter “h,” the letter “u” can also have either a vowel or consonant sound. Thus, depending on the word, you can end up using “a” or “an” as the article. For words that start with the “uh” sound, “an” is the article. For example, you would use “an” before “umbrella,” “unlucky,” “understanding,” and “unbelievable.” Conversely, when the first syllable makes the “you” sound, “a” is the article. Some examples of words that start with “u” and use “a” as the article include “unicorn,” “unanimous,” “university,” and “utility.” English grammar can be confusing. When you’re unsure of which article to use, pronounce the word aloud, and let the sound be your guide. 1. __Vowel sounds__: As a general rule, if the first syllable has an “a,” “e,” “i,” or “o” sound, then use “an.” So you would say “an actor,” not “a actor.” If there is an adjective or adverb in front of the noun, then go off of the first sound of the phrasal verb or first parts of speech. For instance, in the sentence, “Today was an exciting day in New York,” the article reflects the vowel sound in “exciting,” not the consonant sound in the following word. 2. __Consonant sounds__: When you have a singular, countable word that begins with a consonant sound, “a” is the article. Consonant sounds are the phonetics that accompany every letter that is not classified as a vowel. Although the word, “one,” starts with a vowel letter, it has a consonant sound, specifically the “w” sound. Therefore, “one” uses “a” as the article. For example, “a one-hit wonder” is correct, and “an one-hit wonder” is incorrect. 3. __Acronyms, abbreviations, and initialisms__: The same rules apply to acronyms and initials. Pronounce the first syllable of the acronym, and listen for either a vowel or consonant sound. For example, “FBI agent” uses “an” as the article because the acronym is pronounced as a vowel sound, even though the first letter is a consonant. On the other hand, “CIA agent” uses “a” as the article because the acronym is pronounced as a consonant sound. Another example is “an ESL certificate” vs. “a BA.” Become a better writer with the [MasterClass Annual Membership](https://www.masterclass.com). Gain access to exclusive video lessons taught by the world’s best, including Malcolm Gladwell, Neil Gaiman, Walter Mosley, Margaret Atwood, Joyce Carol Oates, Dan Brown, and more. By breaking down the sound of a word, you can determine whether to use “a” or “an” in a sentence.