A/An: Indefinite Articles
The indefinite article takes two forms:
- Use a when the indefinite article comes before a word beginning with a consonant sound: A toy, a book or a house.
- Use an when the indefinite article comes before a word beginning with a vowel sound: An operation, an idea or an apple.
The indefinite article indicates that a noun refers to a general idea rather than a particular thing. For example, you might ask your friend, “Should I bring a gift to the party?” Your friend will understand that you are not asking about a specific type of gift or a specific item. “I am going to bring an apple pie”, your friend tells you. Again, the indefinite article indicates that she is not talking about a specific apple pie. Your friend probably doesn’t even have any pie yet.
The indefinite article only appears with singular nouns. Consider the following examples of indefinite articles used in context:
Example — Please hand me a book; any book will do.
Example — Please hand me an autobiography; any autobiography will do.
Exceptions: Choosing A or An
There are a few exceptions to the general rule of using a before words that start with consonants and an before words that begin with vowels. The first letter of the word honor, for example, is a consonant, but it’s unpronounced. In spite of its spelling, the word honor begins with a vowel sound. Therefore, we use an. Consider the example sentence below for an illustration of this concept.
❌ Incorrect: My mother is a honest woman.
✅ Correct: My mother is an honest woman
Similarly, when the first letter of a word is a vowel but is pronounced with a consonant sound, use a, as in the sample sentence below:
❌ Incorrect: She is an United States senator.
✅ Correct: She is a United States senator.
Using A vs. An with Acronyms
These same rules apply to acronyms:
✅ Correct: A Society of Writers member was quoted in the article.
❌ Incorrect: A S.O.W. member was quoted in the article.
✅ Correct: An S.O.W. member was quoted in the article.
Because S sounds like it begins with a vowel (ess), an should be used in front of it.
Article before an adjective
Sometimes an article modifies a noun that is also modified by an adjective. The usual word order is article + adjective + noun. If the article is indefinite, choose a or an based on the word that immediately follows it. Consider the following examples for reference:
✅ Correct: Eliza will bring a small gift to Sophie’s party.
✅ Correct: I heard an interesting story yesterday.
Indefinite articles with uncountable nouns
Uncountable nouns are nouns that are either difficult or impossible to count. Uncountable nouns include intangible things (e.g., information, air), liquids (e.g., milk, wine), and things that are too large or numerous to count (e.g., equipment, sand, wood). Because these things can’t be counted, you should never use a or an with them — remember, the indefinite article is only for singular nouns —. Uncountable nouns can be modified by words like some, however. Consider the examples below for reference:
❌ Incorrect: Please give me a water.
Water is an uncountable noun and should not be used with the indefinite article.
✅ Correct: Please give me some water.
However, if you describe the water in terms of countable units (like bottles), you can use the indefinite article.
✅ Correct: Please give me a bottle of water.
❌ Incorrect: Please give me an ice.
✅ Correct: Please give me an ice cube.
✅ Correct: Please give me some ice.
Note that depending on the context, some nouns can be countable or uncountable (e.g., hair, noise, time):
✅ Correct: We need a light in this room.
✅ Correct: We need some light in this room.
References
Grammarly. (2021, January 14). Articles. https://www.grammarly.com/blog/articles/
Grammarly. (n.d.). Indefinite Articles: A and An. https://www.grammarly.com/blog/indefinite-articles-a-and-an/