The Indefinite Article with Letters

Rule #1.5: the indefinite article a precedes letters with a consonant sound

He’s a B Student.

His name begins with a K.

Rule #1.6: the indefinite article an precedes letters with a vowel sound

* He got an F on his test.

Her name begins with an A.


Sound is Everything

*Notice that the use of the indefinite article depends on the sound of the letter, not the letter itself.

Exercise 14: Read the letters aloud. Write a before the letters that begin with a consonant sound, and an before letters that begin with a vowel sound.

Initialisms vs Acronyms

The need to know which articles to use when pronouncing individual letters is apparent when comparing their use with initialisms and acronyms. Initialisms are abbreviations that are read letter by letter; e.g. NBA, while acronyms are abbreviations that are read as a word; e.g. NASCAR. Some initialisms are mixed, where the first letter is read as a letter while the remainder is read as a word, e.g. X-ray, U-Boat

Observe how indefinite article use differs between initialisms and acronyms:


He is an NBA player.
She’s an FBI agent.


He’s not a NASCAR driver.
She’s not a FEMA agent.

Exercise 15: Correct or incorrect?

Exercise 16: a or an? Fill in the blanks.