This question already has an answer here:

The indefinite article "an" is used when the following word starts with a vowel sound. For example one write "an adjective" but "a noun".

However, when an abbreviation is used, should this be based on the expanded meaning, or on the letters of the abbreviation.

Specifically, one writes "a noun phrase". However, here on ell.se, the abbreviation "NP" for 'noun phrase" is commonly used. If this were pronounced by sounding out its letters, as "En-Pee" it would call for "an". If it were read as "noun phrase" it would call for "a". Should one write "a NP" or "an NP" here on ELL?

I incline to "a NP" and i used that in an answer just a few minutes ago, but I am not at all sure.

marked as duplicate by J.R. Jul 18 at 1:52

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.


It depends.

As you've identified, it's usually based on the pronunciation. Acronyms will have a common pronunciation which should be followed; a NATO would be correct vs. an N.A.T.O (en-ay-tee-oh) which would be incorrect. Abbreviated notations are another issue though; in the previous sentence "vs." was used and should be pronounced as "versus", and chemical notations like "Li" are read as "lithium".

In your example, "an" would be more correct. "A" can be used as a means of trying to force readers to sound out the full words, however many people would see it as an error. If you choose to use this method, stay consistent throughout your piece of writing.

  • There is only one NATO, so "a NATO" would be very unusual. – Michael Harvey Jul 18 at 10:31
  • NATO would be more of a descriptor, like "a NATO military operation". – Luck Jul 18 at 22:45

Not the answer you're looking for? Browse other questions tagged or ask your own question.