When should I use "a" versus "an" in front of a word beginning with the letter h?

It is a traditional rule of English that an can be used before words that begin with an H sound if the first syllable of that word is not stressed. Indeed, some traditionalists would say it must be used before such words. Since the first syllable of historic is unstressed, it is acceptable to use an before it.

In the Corpus of Contemporary American English, there are 1591 incidences of “a historic” and 428 incidences of “an historic”, showing that usage of an before such words is dying out.

It's pretty hard to decide who is "correct". I can offer the example of someone like newsreader Jeremy Paxman who decidedly says "an historic" with an aspirated "h". There are also lots more television announcers who do this in the UK. It strikes me as being an example of hypercorrectness similar to blanket-removal of linking-r sounds.

My rule of thumb (which I can't prove/cite, but which I'm sure is correct) is to use an for any word that sounds like it begins with a vowel. Both "a history" and "a historian" begin with an H sound. If you slur it into 'istorian, then I would use "an" in spoken sentences (but as that's an incorrect pronunciation anyway you should definitely write it as "a historian."

The point of the word an is to avoid the awkward silent pause between words when saying something like "a apple." So, you should put an before any word that begins with a vowel sound, not just a vowel letter.

The good news is that you just need to do whatever makes sense when talking:

• a historian
• an honor
• a xylophone
• an X-ray
• a user (begins with y sound)
• an umbrella
• a one-eyed pirate (begins with w sound)
• an owl

See this question/answer: When should I use "a" vs "an"?

The question of "a" vs "an" is always decided by the pronunciation of the word that follows the article. Thus, various geographical regions that have different pronunciation rules may use a different article for the same word."

In short, if you pronounce the "h" then use "a". If you do not pronounce the "h", use "an."

In words beginning with “h” where the accent is on the 2nd syllable, it is also correct to use "an". In such cases you do not pronounce the “h”.

So "an historical act" is spoken as "an'istorical act".

This practice has a long, respected pedigree, at least in British literature.

Holy Moly (Or Oly Moly):

Google books ngram viewer for "a historic" and "an historic"

An or a, that is the question. I find that if I don't think about it I automatically say the word with whichever article sounds best. The hard bit is micro-analyzing it. (P.S. I also automatically write it in whichever way sounds best as I 'speak' it in my head). There is no clearly defined 'correct' answer as history and geographical location / accents mean the goal-post keep moving.

If you pronounce the h, say a historian. If you don't pronounce the h, say an historian. The latter sounds old-fashioned now.

It depends. In contemporary usage, if the "H" is voiced, as in "house" or "happy", the article "a"is becoming more common, for example, "He is a humble man". if the "H" is not voiced, as in "honest", or "honorable", an is still generally preferred.

In older texts, it is more common to have "an" in places where contemporary usage favors "a". Psalm 84:3 (Protestant versification) talks about the sparrow finding "an house" in the Jewish temple.

I use "an" before a word which I think would start with a vowel in the speech of whoever I'm talking to. For instance, I ordinarily say "an" before "historical", because although I always pronounce "h" at the beginning of "historical", I believe that many people don't pronounce an "h" here. I just want to get along.

The choice of article is based on pronunciation, not spelling, so for instance "an honor". There are some dialects in which the h in "historical" is silent, and for those dialects, "an historical" is correct.

You ask why some people say or write an historical. The thing is, that's not what any people actually say or write. People who uses the string an historical is going have a noun after it. E.g, novel:

• He started an historical novel today and now he can't put it down.

because an historical is not a complete constituent; it has to have a noun to modify. But an historical novel is a complete constituent. And in that constituent, you will notice that the stress is on the syllable with TOR in it.

• an hisTORical novel

And you will also notice that the syllable with his in it is not stressed, and that there is a strong tendency to leave out the /h/ when saying it, producing something that might be pronounced

• /ənɪ'storəkəl'navəl/,

and might be spelled

• an 'istorical novel

if one had the simple faith in apostrophes that millions display daily.

A linguist would say (and this linguist does say) that initial /h/ is frequently dropped before unstressed syllables. Stressed initial syllables are more normal in English than unstressed, and so they don't drop /h/; these include all monosyllables like ham and hint, for instance.

This is not a rule that has to be followed; this is an optional rule that is followed by many people, but not by all, often, but not always, even by the same people. So sometimes people say "an historical", because 'istorical starts with a vowel in speech, and the rule says an before vowels when they're pronounced as vowels in speech, never mind spelling. So in those cases they'll write it an historical, too, because it's a speech rule, not a spelling rule.