When I was writing out a degree title, I recall the "rule"
"a" comes before a consonant
"an" comes before a vowel
but then I naturally used to say that "I have an MSc degree" just for ease of pronunciation.
as M is a consonant, I thought this violates the "rule" but "an" is apparently the appropriate indefinite article for "MSc".
Why do I use "an" and not "a" ahead of a degree title as above?