R is a consonant (indicating “a”) but also if you say the word R it starts with a vowel (indicating “an”)
both look wrong :(
R is a consonant (indicating “a”) but also if you say the word R it starts with a vowel (indicating “an”)
both look wrong :(
Any type of abbreviation follows the same rules as any other word. If it starts with a vowel sound, use an.
I think an RTS looks fine and a RTS sounds odd.
Edit: Forgot a source