a, an, the

“A” and “an” signal that the noun modified is indefinite, referring to any member of a group. For example:

• “My daughter really wants a dog for Christmas.” This refers to any dog. We don’t know which dog because we haven’t found the dog yet.
• “Somebody call a policeman!” This refers to any policeman. We don’t need a specific policeman; we need any policeman who is available.
• “When I was at the zoo, I saw an elephant!” Here, we’re talking about a single, non-specific thing, in this case an elephant. There are probably several elephants at the zoo, but there’s only one we’re talking about here.

 

Note: because A and An means one, they cannot be used in  plural. For example:

• singular
  • a chair, a city, a manager
• plural—CANNOT BE USED

 

It’s all about how it sounds!

 

Consonant or vowel sound?

 

a + singular noun beginning with a consonant:

• a boy
• a car
• a bike
• a zoo
• a dog

 

an + singular noun beginning with a vowel:

• an elephant
• an egg
• an apple
• an idiot
• an orphan

 

a + singular noun beginning with a consonant sound:

• a user (sounds like ‘yoo-zer,’ i.e. begins with a consonant ‘y’ sound, so ‘a’ is used)
• a university
• a unicycle

 

an + nouns starting with silent “h”:

• an hour
• an honest man

 

a + nouns starting with a pronounced “h”:

• a horse
• a human response

 

In some cases where “h” is pronounced, such as “historical,” you can use an. However, a is more commonly used and preferred. For example: A historical event is worth recording.

Acronyms

Introductory Composition at Purdue (ICaP) handles first-year writing at the University. Therefore, an ICaP memo generally discusses issues concerning English 106 instructors.
Another case where this rule applies is when acronyms or initialisms start with consonant letters but have vowel sounds:

• An MSDS (material safety data sheet) was used to record the data.
• An SPCC plan (Spill Prevention Control and Countermeasures plan) will help us prepare for the worst.

 

With adjectives

If the noun is modified by an adjective, the choice between a and an depends on the initial sound of the adjective that immediately follows the article:

• a broken egg
• an unusual problem
• a European country (sounds like ‘yer-o-pi-an,’ i.e. begins with consonant ‘y’ sound)

 

Membership in a group

In English, the indefinite articles are used to indicate membership in a group:

• I am a teacher. (I am a member of a large group known as teachers.)
• Brian is an Irishman. (Brian is a member of the people known as Irish.)
• Seiko is a practicing Buddhist. (Seiko is a member of the group of people known as Buddhists.)