I haven’t had a copyediting post in a while, so let’s talk about “a” and “an.” We pretty much all know that “a” is to be used before a consonant sound and “an” used before a vowel sound, right? That seems fairly straightforward, but in reality it gets a bit dicey because of the way people actually pronounce words. Many Americans use the combination “an historical” with the thought that it’s actually more correct, because that’s how many folks from the UK say it. However, Brits don’t pronounce the “h” the way that Americans do. For an American, “a historical” is actually the correct usage.
Similarly, many people look down on American dialects that use “a” before words like “apple.” However, in those dialects, the “apple” is actually pronounced with a consonant sound. Hear that glottal stop way down in your throat that starts the “uh” in “uh-oh”? That’s a consonant (regardless of whether English has a letter for it) that starts words like “apple” in some American dialects, and the “a” that those speakers use in front of the word is completely natural, if not grammatical.
So if you’re speaking American and are using “an historical” as a matter of course, you’re actually doing a bit of societal hypercorrection. And copyeditors need to realize that “a apple” might actually most closely resemble a character’s native speech.
I'm a freelance copyeditor specializing in fantasy and science fiction. SF/F novels I have copyedited have been finalists for (and have sometimes won) the Hugo, Nebula, Arthur C. Clarke, Endeavour, Golden Spur, John W. Campbell Memorial, Quill, Locus, Philip K. Dick, British Science Fiction, British Fantasy, and World Fantasy awards. In 2007 I became the first and only copyeditor ever short-listed for a World Fantasy Award.