The rule of thumb taught in grammar school was simple – use ‘a’ before words beginning with consonants and ‘an’ before words beginning with vowels. Simple, no?
Well, here’s one – ‘an’ before words beginning with ‘h’ (e.g. ‘an historian’). I’ve never really know what to do with this one. It’s always kind of bugged me, since it violates the basic rule I was taught as a younster but it also made a kind of sense, especially when you read the two words aloud.
Likewise, you run into similar situations with acronyms and abbreviations. Try following the rule and see what you get. Need an example? Here you go: “I just back from a SF convention.” Now, following the law of the land, this is grammatically correct. ‘SF’ begins with a consonant; therefore, you must lead with ‘a’. Or do you? If you read that phrase aloud, you run into a minor awkwardness – ‘SF’ is pronounced with a leading vowel sound. ‘Ess-eff.’
“Jack Lynch”:http://andromeda.rutgers.edu/~jlynch/Writing/a.html has this to say about the subject:
bq. Use an in place of a when it precedes a vowel sound, not just a vowel. That means it’s “an honor” (the h is silent), but “a UFO” (because it’s pronounced yoo eff oh). This confuses people most often with acronyms and other abbreviations: some people think it’s wrong to use “an” in front of an abbreviation (like “MRI”) because “an” can only go before vowels. Poppycock: the sound is what matters. It’s “an MRI,” assuming you pronounce it “em ar eye.”
Sound advice, and a rule of thumb that I’ve leaned toward for a little while. I know that not everyone does – I’ve seen an equal number of people writer ‘a SF convention’ as ‘an SF convention’.
Of course, the other problem is when people read acronyms as the full word. Instead of reading ‘an SF convention,’ some people read ‘an science fiction convention,’ returning the sentence back to grammatical awkwardness. I think it is probable, though, that far fewer folks do this than those who read the acronym as the acronym.
What about you? How do you handle acronymns and abbreviations in your writing, and how do you read them?