It can be a bit confusing figuring out where indefinite articles a and an are used. This is the correct way to use them. Note to the reader:
The rules for a and an may change in different countries. These rules are based on United States English and may or may not apply elsewhere.
Steps
Method 1 of 2: Use "a" Correctly
Step 1. Use a before all words that begin with a consonant sound
In English, almost all words that begin with a consonant will be preceded by the article a.
For example: a pet, a door, a green onion, a cat, a hysterical joke
Step 2. Understand that there are some exceptions to this rule
Some words can be written beginning with a vowel, but are pronounced with initial consonant sounds. Words that start with h, y, u, and eu or e are common words that can cause confusion.
- Use a when the u makes the same sound as the y in you: a union, a unicorn, a used napkin, a usability study.
- Use a when the o makes the same sound as the w in won: a one-legged man.
- Use a when eu or e makes the same sound as the y: a European trip, a ewe lamb.
- Don't use a when h is silent.
Step 3. Read the words out loud if you are not sure
Sometimes the way the word looks on the page is not enough to know which article to use. Read the word out loud, in a way that sounds appropriate to you, and then use the article based on that.
Method 2 of 2: Use an Correctly
Step 1. Use an before all words that begin with vowel sounds
In English, almost all words that begin with vowels will be preceded by the article an.
For example: an apple, an elbow, an Indian
Step 2. Understand that there are also some exceptions to this rule
Some words can be written beginning with a consonant, but are pronounced with the initial vowel sound. Words that start in h are the most common causes of confusion, but there are some other letters that can also be challenging.
- Use an before a silent h: an hour, an honorable peace, an honest error.
- It uses an before words that are written with a consonant, but are pronounced with a vowel sound: an MBA.
Step 3. Understand that pronunciation can vary depending on geographic location
For example: the British and American pronunciation of certain words change a lot, especially in words that start with h like herb. In American pronunciation, h is silent, so the correct form would be an herb. But in British pronunciation, the h is pronounced, so the correct use would be a herb.
Step 4. Understand that the word historic is a special case
There is considerable debate as to whether the correct use is a historic event or an historic event. Almost all style manuals and usage guides prefer historic event, citing the consonant sound explanation given in this article. However, you can see that from time to time an historic comes up, especially among British writers.
Some American writers also use an with fairly long words (three or more syllables) beginning with H, when the first syllable is not stressed: an hypothesis, an habitual offender
Advice
- It's interesting to note that these rules for a and an also apply to the word the. Although the is always spelled the same way, the "e" in that word can be pronounced either as in umbrella or as in me. Normally (when you would use a), it is pronounced as in umbrella. But when you would have to use an, you must pronounce it as "say" (as in the word me).
- A and an are indefinite articles, which means that they do not refer to a particular or special word. If you need a vehicle to go to work, but any car would be fine for you, you would say: I need a car. If you need a very specific car, like one you share with your roommate, you would say: I need the car.