Disclaimer: if you're from the UK, all bets are off and you may be excused. You guys speak y'alls language, and I'll speak mine.
But if you're an American guilty of this, please report to the nearest American-born English professor worth his salt, apologize and beg to be taught proper Americanized English.
Now for a brief while, the correct usage of indefinite articles stumped me on a few occasions. In my head, I just knew certain combinations sounded right, and others were just plain abominations. So why did people insist on using those abominations? Was I crazy?
I know better than many that language is a continually evolving thing, subject to assaults from ivory towers to the scummiest ghettos. But on some occasions, certain changes are good. This however, is one of those issues that seems to be in conflict, precariously teetering between all that is good and all that is pure evil.
I posit that we should use "a" for every word beginning with a consonant sound--this is uncontroversial. Furthermore--and here is where I depart from the language murderers--that historical, hypothesis, habitual and all their variations begin with a clear H sound, as it sounds in the words hot, heavy, happy, hill, and so on. Of course not all words beginning with H have the H sound. An honorable man might make an honest mistake. Clearly these start with a vowel sound and require an "an."
Now I understand if you were using "an" if you pronounce "historical" as "istorical," or "hypothesis" as "eye-pothesis" but that is saying it all wrong. That would be an honest mistake. Therefore, "a" should precede the aforementioned words when an indefinite article is appropriate.
All the American grammar checkers out there should be updated. An historical event=wrong. A historical event=correct. I mean, do you ever ask for an hot cup of coffee? Even Microsoft Word says that's wrong.
*With a little observation of common formal American English, it isn't so indefinite now is it?