Which is correct?
An enhanced driver’s license contains _______ that allows authorities to pull up your data.
a. a RFID tag
b. an RFID tag
The official pronunciation of RFID is R-F-I-D — saying the letters of the initialism separately. However, if something can be said in two syllables rather than four, that’s usually going to happen (and who am I to argue, since I pronounce ASAP as A-sap). RFID is commonly pronounced ARE-fid. Whether you pronounce the letters separately, though, or say are-fid, “an” is the correct article because both sound as if they start with a vowel.
There are also those who pronounce RFID as RIFF-id or RIFF-dee. If that’s how you pronounce it, you could write a RFID but be aware that most people would read that as “a ARE-EFF-EYE-DEE” or “a ARE-fid,” which would not leave a good impression of your intelligence. Try saying them out loud and you’ll see what I mean.
The Urban Dictionary discusses RFID, including its pronunciation.
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