What Is the Indefinite Article? (with Examples)

Indefinite Article

The indefinite article is the word a or an. It is used before a noun to define it as something non-specific (e.g., something generic or something mentioned for the first time).
  • I'm a murderer.
  • (This means an unspecified murderer, i.e., not one previously discussed.)
The indefinite article contrasts with the definite article (the), which defines something as specific (e.g., something previously mentioned or known, something unique or something being identified by the speaker).
  • I'm the murderer.
  • (This means a specific murderer, i.e., the one previously discussed.)

More about the Indefinite Article

Articles are classified as determiners. A determiner sits before a noun to indicate quantity, possession, specificity or definiteness.

There are two types of articles: These sentences compare the use of indefinite and definite articles:
  • Pass me a hammer.
  • (The hammer is non-specific; i.e., any hammer will do.)
  • Pass me the hammer.
  • (The hammer is specific. It's the hammer known to the speaker and the listener; e.g., the one they've just been using.)
  • I need a chair.
  • (any chair)
  • I need the chair.
  • (a specific chair)

Why Should I Care about Indefinite Articles?

There are two commonly discussed issues related to indefinite articles.

(Issue 1) Choosing an or a.

An is used before a vowel sound, and a is used before a consonant sound. (The important word here is sound.) Lots of words and abbreviations that start with vowels (typically u) start with consonant sounds (e.g., unicorn, unique, united, Ouija, one-off), and lots of abbreviations that start with consonants start with vowel sounds (e.g., MOT, LRS, NTU).
  • An MoD official and a MAFF official visited an NBC facility of a NATO country.
  • (The M and the N of the initialisms MoD (Ministry of Defence) and NBC (Nuclear Biological and Chemical) are pronounced "en" and "em", i.e., with vowel sounds. The N and M of the acronyms NATO (North Atlantic Treaty Organization) and MAFF (Ministry of Agriculture, Forestry and Fisheries) are pronounced "nuh" and "muh", i.e., with consonant sounds.)
  • I had a unique opportunity to strike an unexpected blow.
  • (Unique attracts a because it starts with the consonant sound "yuh". Unexpected attracts an because it starts with a vowel sound "uh".)
These examples prove that it's all about how the word after the indefinite article sounds and not necessarily whether its first letter is a vowel or a consonant.

(Issue 2) Writing a job title or an office name with a lowercase letter.

A job title (e.g., president, judge, director) or the name of office (parliament, court, accounts section) is written with a lowercase letter when the word is being used in its dictionary definition (i.e., as a common noun). Some writers are tempted to give such terms capital letters either because the terms seem important (a terrible reason to give a word a capital letter) or because they become confused, knowing such terms can be written with capital letters when they refer to specific people or offices.

If the job title or office name is preceded by the indefinite article (an or a), there is a high chance it is being used in its dictionary definition (i.e., not as proper noun), in which case you must write it with a lowercase letter.
  • The Prime Minister said: "Being a prime minister is a lonely job... you cannot lead from the crowd." (Prime Minister Margaret Thatcher). [correct]
  • (Here, The Prime Minister specifies an individual, but a prime minister does not. It is just the dictionary definition of the term prime minister. In other words, the first one is a proper noun, but the second is a common noun.)
Read more about articles.

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See Also

Take a test on indefinite articles What is the definite article? What are adjectives? When to use an and a Glossary of grammatical terms