Does the grammar rule a and a(n) with vowels apply to speaking?

of course. speaking or writing, the rules are the same.

Yes. But keep in mind that the rule is for vowel sounds, not vowel symbols. So we talk about “a unique opportunity,” rather than “an unique opportunity,” because “unique” starts with a consonant sound (“y”) even though it starts with a vowel symbol (“u”). This is the same reason that some people say “a historic event” while others say “an historic event.” It all depends on whether they aspirate the “h” or not. If they don’t, then “historic” is more or less pronounced “istoric,” which makes “an” appropriate. But if the “h” is aspirated, then just “a” is appropriate.

Yes.

The rule exists to help in speaking. It is difficult to pronounce two vowels in a row. You would need to pause between them. The n provides a transition between the two sounds.

Spanish has a lot of words that end in vowels. It is considered proper to slur the vowel sound at the end of a word with the vowel sound at the beginning of the next one, so they count as a single syllable.

It makes an big difference. Only a idiot wouldn’t use them.

Yes of course… except I don’t use the “treat H like it isn’t pronounced” part, unless I’m imitating an accent that doesn’t pronounce it.

I think “an history book” sounds and looks irritatingly silly to me. I’d rather say and write “an ‘istory book” than that, but what I do say and write is “a history book” because I pronounce the H and I think that aspect of English is annoying and worth rebelling against.

^Never heard anyone saying “an history book” .

I have heard people say “an historic event”. The letter h seems to be a special case. Try making an h sound by itself. It seems to be begging to be followed by a vowel.

I’m surprised to see an Oxford English Dictionary web site article that actually supports my opinion and says it is changing.

When I was at university (decades ago now) it was still taught that “an historic” was correct.

It still sounds right to me, though I would agree that “a” should be used for the other cases where the h is pronounced. I have never seen or heard “an” being used for any of them.

Just try saying “a historic” without pausing. I can’t do it. I don’t have that problem with “a horrific”.

@LostInParadise I wrote sloppily in my first reply here. It’s always been the rule that you use “a” with H when it it pronounced: a hose, a hat, a habit

According to this article it’s actually about the emphasis being on the second syllable, which apparently used to result in an H not being pronounced (...), and the “an convention” lasting longer than the previously-silent H on those words.

So I (hehe) would say my instinct is correct that saying “an historic” would make more sense as “an ‘istoric” ... in my mind it goes along with the accent that would also say “an ‘orse” (conjuring Pygmalion & Audrey Hepburn in My Fair Lady).

Does the grammar rule a and a(n) with vowels apply to speaking?

Yes, it primarily applies to speaking, and secondarily to writing.