"A homomorphism" or "an homomorphism"

Question

Which one of these constructions

• An homomorphism

• A homomorphism

is correct in American English?

I see both uses in research paper. Also the wikipedia page uses both construction in the same article.

Answer 1

The latter sentence is correct in American English. The consonant h is sounded in the word "homomorphism."

Answer 2

It's technically not wrong to put "an" before H even when it's not a silent H. A common example we often see is "an history." The "an" before a hard H, however, is something you usually only see in old texts, extremely formal writing, or in academia, although not consistently in academia. Also, the "an" before a hard H isn't limited to the UK. My high school history textbook was titled An History of the United States.

Here are some other examples:

• "an hero"
• "an human"
• "an homomorphism"

All of that said, unless you are some academic writing a doctoral thesis or a textbook or you have some style guide telling you to use "an," I would use "a" instead. It isn't wrong, and it won't be question by those who aren't aware of this rare and highbrow use of "an" before a hard H.

Incidentally, when you see "an" before a hard H, you will often notice that it isn't applied universally in the writing. The author will only use it before certain words that they want to give particular homage or reverence to, or even just one such word, like if they're writing a history textbook, using "an" before "history," but before every other H word that has a hard H, like "hill" or "hope" or whatever, they will still use "a."