“A” or “An” before an Abbreviation?
Use a or an before an acronym or other abbreviation depending on how it is pronounced, not how it is written. If the abbreviation starts with a consonant sound when read aloud, use a; if it starts with a vowel sound, use an.
This rule applies regardless of whether the first letter is a vowel or a consonant when written down.
- a NATO member but an NBA player, an NFL match
Even though both abbreviations begin with “N,” the acronym NATO (pronounced “NAY-toh”) begins with a consonant sound, while NBA (pronounced “en-bee-AY”) begins with a vowel sound.
- a NICU doctor but an NFT, an NGO
- a SARS vaccine but an SOS
- a FICA contribution but an FBI agent
- a HEPA filter but an HTML file
- a LAN password but an LED screen
- a MoMA curator but an MBA program, an MNC
- an ATM but a UFO, a UNIX command
- an EU mandate but a US senator, a UK resident
- an OPEC report but a UN resolution
- a DOS file but a DNR
- an EST clock but a UTC or a GMT clock
Read the abbreviation aloud. An abbreviation may begin with a consonant letter in writing but be pronounced starting with a vowel sound (NFT, SEO, LED), or begin with a vowel but be read aloud starting with a consonant sound (UK, US, EULA). Note how in the following example, a is used before the abbreviation, even though an is used with the full form.
- an unidentified flying object
buta UFOpronounced “a YOO-ef-OH” (/ˌjuːɛfˈəʊ/)
Depending on how an abbreviation is read aloud, it may be either an initialism or an acronym.
With initialisms
Use an before an initialism that begins with a vowel sound, even if the first letter is a consonant when written down. (An initialism is an abbreviation of which the letters are individually pronounced.)
- an HR manager
- an SEO expert
- an XML file
- an MVP award
- an NDA
- an NFT
- an NBA player
- an RDF
But if the initialism begins with a consonant sound and is pronounced as such, it takes a instead of an as usual.
- a PTA meeting
- a BLM protest
- a CEO
- a DIY project
- a DNA study
- a TBT photo
- a KRA
- a YMCA hostel
- a PDF editor
If the initialism begins with a vowel (like “U”) but starts with a consonant sound when read aloud, use a instead of an.
- a UFO
- a URL
- a USB drive
- a US city
- a UK delegation
- a UN representative
- a UPS delivery
And if the initialism both begins with a vowel and starts with a vowel sound when pronounced, use an as usual.
- an ATM
- an EMS worker
- an IRS notice
- an OTC medication
With acronyms
With acronyms, which are abbreviations pronounced as words, make sure to follow the rule of using a or an depending on whether the acronym starts with a consonant or a vowel sound. The first letter of an acronym may be a vowel, but if it is pronounced with a consonant sound, use a instead of an.
- a EULA (“YOO-luh”)
- a EUCOM committee
- a UEFA game
- a UNICEF program
- a UNESCO initiative
But if an acronym begins with a vowel sound, use an.
- an OPEC report
- an ASCII value
- an ECHO employee
- an ISDA agreement
- an ULTRA official
If an acronym begins with a consonant sound, use a instead of an as usual.
- a NATO decision
- a BAFTA award
- a COVID patient
- a FICA contribution
- a LAN router
- a NAFTA committee
- a PETA supporter
- a radar operator
- a SARS vaccine
- a XERT experiment
Examples from published content
Here are some examples from published content that illustrate how a or an is used before an acronym or other abbreviation based on how it is pronounced.
An NFT, or a nonfungible token, is a digital file created using blockchain computer code.
— “Teens cash in on the NFT art boom,” New York Times (Aug. 14, 2021)A NATO post would give him additional command experience.
— “Pentagon weighs top Iraq general as NATO chief,” New York Times (Jan. 21, 2008)The International Aids Society said Mr Brown gave the world hope that an HIV cure was possible.
— “First person cured of HIV, Timothy Ray Brown, dies,” BBC News (Sep. 30, 2020)Venus shining bright and low has been reported many times as a UFO.
— “Identifying UFOs,” NASA website (Accessed Feb. 8, 2021)The DMD projection system consists of an LED light source with a collimating lens.
— “Tomographic near-eye displays,” Nature (June 7, 2019)
And while use of a or an depends on how an abbreviation is pronounced, use of the article the depends on convention and accepted usage (the BBC but the PBS). Read more in this article on whether the should be used before an abbreviation.