It’s an F. Since the consonant F begins with a vowel sound (eff), it takes the article "an".

It’s an F. Since the consonant F begins with a vowel sound (eff), it takes the article an.

I got an F on my exam.

I got a F on my exam.

Remember, the choice between "a" and "an" is driven by pronunciation—not spelling, so use "an" with consonants that are pronounced with a vowel sound (F, H, L, M, N, R, S, and X).

The aircraft was followed by an F-16 fighter plane.

Use also the article "an" before acronyms that begin with F and are pronounced as individual letters; for example, we say:

• an FBI... (Federal Bureau of Investigation)
• an FDA... (US Food and Drug Administration)
• an FYI... (For Your Information)
• an FBR... (Foundation for Biomedical Research)
• etc.

My father has been an FBI agent since 2011.

Other acronyms, however, are pronounced as words, including:

• FAANG (Facebook, Amazon, Apple, Netflix, and Google)
• FIFO (First In, First Out)
• Fmr. (Former)
• FOREX (Foreign Exchange)
• etc.

And they take the article "a" if the initial sound of the word is a consonant.

A FIFO file is similar to a pipe.