Because saying ‘H’ starts with an ‘ay’ sound.

What matters is not whether or not the first letter is a consonant, but whether the first sound is a vowel or a consonant sound. In this case, “H” is actually pronounced like “aych”, so it sounds like it begins with a vowel.

Pass me an M&M.

@Harp: You did it better. I am shamed.

@asmonet- Tell you what: I’ll let you be ponderous, thorough and balding for awhile if I can be the quick, witty, pretty one

H’s in English are either aspirated or unaspirated. How they evolved is another linguistic mystery. A good source

Any word beginning with an aspirated “h” (one that’s sounded when spoken) always takes “a”. For example, a hotel, a holiday, a history professor, and a historic treaty.

Any word beginning with an unaspirated “h” (one that isn’t sounded when spoken) takes “an”. For example, an hour, an heir, an honour, and depending on dialect an herb. In fact these four words (and their derivatives) are the only common English terms that fall into this category. Oops. Make that five. An honest mistake.”

@gail Nice pun.

I can’t take credit for that wry quip. It is a quote from the Source that I linked.

There’s also a distinction to be made between acronyms that we pronounce letter by letter (such as HDTV) and those that we pronounce as words (such as LAN). If we were to name the letters in LAN, they’d be ell-ay-en, and we’d say “an LAN.” But we don’t. We pronounce “LAN” as if it were a word spelled “lan.” And so in that case, even though the first letter (L) is named in English beginning with a vowel sound (“ell”), we’d say “a LAN” and not “an LAN.”

And there are some acronyms, especially in high-tech, that you can’t tell about by sight. You just have to know the convention. For example, you might think SCSI would be pronounced “ess-see-ess-eye,” but it’s not. We say “scuzzy.”

Some of us say “an S-M-E” for a subject-matter expert (SME), and some say “a smee.”

@gail
I wonder why we bother to say “unaspirated H” instead of just “silent H”. We don’t say “unsibilated S”.

@Harp, if it’s just one, why isn’t it an M?

who said I wanted just one?

Thanks for some good replies. At least there are some governing rules that make sense. In danish we have ‘en’ and ‘et’ instead of ‘a’ and ‘an’. And there basically isn’t any regulation as to what to use when, so you’ll pretty much have to memorize it for every single noun :-)

@ Harp and Jeruba.. pretty funny! But she’s got you.. you did say: Pass me an M&M. hee hee!!

@Harp, I’ll pass you an M & then another M. How’s that?

Red, please

Here.

SCORE!

@Harp: In that case, instead of acting out Freaky Friday, how bout we forget the whole thing at eat cookies? :)

M&M cookies?

Deal!

Harp (or Arp, if you prefer): These words, among many others, sprang, unaided, from the head of Zeus. Some examples:

Fricative
Glottal Stop
Smooth and rough breathing (Greek)
Schwa
Plosives
Bilabial
Dental
Alveolar
Palatal
Velar

From Wickipedia

“The spiritus lenis (Latin for “smooth breathing”; Greek: ψιλὸν πνεῦμα psilòn pneûma or ψιλή psilī́) is a diacritical mark used in the polytonic orthography. In ancient Greek, it indicates the lack of initial aspiration, or the absence of the voiceless glottal fricative (/h/) from the beginning of a word.”

In other words, I haven’t a clue. Love “voiceless glottal fricative” however.