A or An

A or An 

a /ei/ (weak form: /ə/ is usual) / an /ən/ weak form: /æn/ is usual) (determiner)

A / an is called the "indefinite article". [See Articles]

In some cases, the letter "a" is always pronounced /ei/ as in a, b, c,....; A, B, C,....)

See the details of how A / An is used below.

1. When to use a or an

We use "a" before a consonant sound. It is usually pronounced with the neutral vowel /ə/. See the examples below.

• He's a /ə/ teacher. 

Image by Sasin Tipchai from Pixabay

• What a /ə/ nice car!

Image by Dariusz Sankowski from Pixabay

We use "an" before a vowel sound. It is usually pronounced with the neutral vowel: /ən/. See the examples below.

1. He's an /ən/ actor.
2. What an /ən/ amazing day!
3. It takes an /ən/ hour to complete this job. *
4. I met an /ən/ honest person at the cinema. *

* In examples 3 and 4, the letter "h" is silent. Although it's a consonant, it has no sound here.

You can see [An] and [Consonants and vowels] for more details.

2. A or An comes before a singular countable noun

Form1: a/an + singular countable noun

Example: a book, a university, an idea, etc.,. 

Form2:  a/an + modifier(s) + singular countable noun

Example: a brave boy, a very famous actor, an amazing new website, etc.,.

Note: A / an has no plural form. We use either no word at all or some in the plural instead. [See Some and Zero Article for more details]

Let's see: This is a dog. This is a book. 

Image by Marek from Pixabay

And let's see: These are some books.

Image by Ylanite Koppens from Pixabay

In order to find out how to choose between Some and Zero Article, see Zero Article 2.

3. The meaning and use of a / an

A or an means any one of a kind or group. It contrasts with "The" (the definite article) and Zero Article. In order to see how these are used, go to ["The" in section 3] and [Zero Articel]. It means singular but not unique.

3.1 Use after the verb "be" in naming a person's job

Example: 

Person 1: What does your brother do (for a living)?

Person 2: He's a farmer.

Person 1: Oh, really? Mine's an architect. (not: Mine's architect.)

3.2 Use when something is mentioned for the first time

Example: 

1. I have a very old bike. But the bike is very durable. *

2. I bought an old book from a bookstore. Although the book is very old, but it didn't take me too long to get to the bookstore. *

* When something is mentioned again and again, we use "the" instead.

3.3 Use when it contrasts with two, three, etc., it means one

Example 1: I'd like two pieces of pizza and a glass of coke, please.

Image by Bruno /Germany from Pixabay

Example 2: Your father stayed in Bangkok for a week and mine for 2 weeks.

3.4 Use in front of "Numbers" instead of one

Example: 

1. a half = ½ or 0.5

2. a third = ⅓ or  0.33

3. a couple = 2

4. a dozen = 12

5. a hundred = 100

6. a million = 1,000,000

3.5 In phrases of "Measuring" and "Frequency", it means "per" or "every"

1. Once a day = one time per day

2. Twice a day = two times per day

3. Four times a week = four times per week

4. Ten times a year = ten times per year

Example: I go to the gym once a week. He plays football 4 times a month.

3.6 Use in general use

A or An can be used to describe "all examples of the same kind", or "any example of the same kind".

Example:

1. "What is an apartment?" "An apartment is a building in which people live."
2. A student has more capability than a farmer. 
3. We can use many ways to learn a programming language.

4. Special uses of a or an

4.1 Special use with an uncountable noun and zero article

It's not used to describe substances, masses, or abstractions in general. For example, we don't say: He gave my friend a good advice.

4.2 Special use before "Quantity words" and "Adverbs of Degree"

Let's see these:

1. a bit (of)
2. a few (of)
3. a little (of)
4. a large quantity (of)
5. a (great) deal (of)
6. a considerable number (of) [formal]
7. a lot (of) [informal]

For example: A few voters attended the election. Or: A lot of voters attended the election.

4.3 Special use before "Part nouns", "Unit nouns", and "Nouns of kind"

A. Before "Part nouns"

For example: a piece of cake, a slice of pizza, etc.,.

B. Before "Unit nouns"

For example: a glass of coffee, a cup of sugar, etc.,.

C. Before "Nouns of kind"

 For example: a type of book, a kind of drink, etc.,.

Note: we usually omit the second a which would come before a countable noun after "a kind of", "a type of", "a sort of". Let's see an example: A Camry is a type of car. (NOT: a type of a car)

4.4 When some determiners such as "what, such, and many" are used with a singular countable noun

Form: What/such/many + a + singular countable noun

For example:

1. What a cat!
2. It's such a cool phone.
3. Many a student joined the video conference. 

Note: there's another special use of a or an when it follows the adverbs "quite" and "rather". For example: We had rather a nice car. Or: We had quite a nice car. (Also: ... a rather nice car.)

We hope this article helps you understand and know how a or an is used. For other topics, you can click on the links to find out about them.