When to Use A or An Before Acronyms (2024)

Today’s lesson is a quick tip about how to choose the correct article (a/an, called “indefinite articles”) before an acronym. These articles are occasionally swapped, and it’s easy to see why! Choosing the article may seem simple based on whether the acronym stars with a consonant or vowel, but usage depends on how the subsequent word is pronounced, not spelled.

What does this mean?

The patient underwent a/an MRI scan.

When we see MRI written, we mentally say each letter—em are eye—rather than “magnetic resonance imaging.” Which article should it get?

Since the letter M is pronounced starting with a vowel (em), we use the article that goes with vowel sounds: an.

The patient underwent an MRI scan.

And what if we didn’t use the acronym but wrote the term out?

The patient underwent a magnetic resonance imagingscan.

This time, the subsequent word (magnetic) starts with a consonant sound, so we use “a.” Make sense?

Here are some other examples:

You get the idea!

If you’re stuck with figuring out what article to use before an acronym (or any word), just say it out loud. Its pronunciation determines which article it receives—nice and straightforward.